Add binary lists and binaries for micronodes

[philippguertler]

The API for getting or creating binaries is as follows:

OpenAPI 3.0.2 Specification

openapi: '3.0.2'
info:
  title: Gentics Mesh
  version: '2'
paths:
  '/{project}/nodes/{nodeUuid}/binary/{fieldPath}':
    get:
      summary: Downloads a binary from a node.
      responses:
        200:
          description: "A binary file"
    post:
      summary: Uploads a binary to a node.
      requestBody:
        content:
          multipart/form-data:
            schema:
              type: object
              properties:
                language:
                  description: Language of the node content which contains the binary field which should be updated.
                  type: string
                version:
                  description: Version of the node which should be updated. This information is used to determine conflicting updates.
                  type: string
                binary:
                  description: Single binary file part.
                  type: string
                  format: binary
                listMode:
                  description: >-
                    How the binary should be inserted into a list. This is ignored if the path is not a list.
                    The following modes are available:
                    
                      * `append` - Appends the binary to the end of the list.
                      * `prepend` - Puts the binary to the beginning of the list, increasing the index of all other elements.
                      * `insert` - Inserts the binary to the given index, increasing the index of all subsequent items.
                      * `replace` - Replaces the binary at the given index.
                    
                    `insert` and `replace` can only be used when an index for the binary list field is provided in the `fieldPath` path parameter.
                    The index in `fieldPath` is ignored if the mode is `append` or `prepend`.
                    The default value is `append` if the {fieldPath} refers to a binary list, `insert` if it refers to an element inside a list.
                  type: string
                  enum: [append, prepend, insert, replace]
      responses:
        200:
          description: "The node response of the updated node."
        400:
          description: "Invalid listMode."
    parameters:
      - $ref: '#/components/parameters/projectParam'
      - $ref: '#/components/parameters/nodeUuidParam'
      - $ref: '#/components/parameters/fieldPathParam'
components:
  parameters:
    projectParam:
      name: project
      in: path
      description: The project of the node.
      required: true
      schema:
        type: string
    nodeUuidParam:
      name: nodeUuid
      in: path
      description: The uuid of the node.
      required: true
      schema:
        type: string
    fieldPathParam:
      name: fieldPath
      in: path
      description: >-
        `{fieldPath}` describes the location of a field inside a node. All indices for list fields are zero-based.
        This table gives examples for all cases:
  
        |  Field                              | 
        Path                                                                      
        |  Example              |
  
        |-------------------------------------|-----------------------------------------------------------------------------|-----------------------|
  
        | Field                        |
        `{fieldName}`                                                              
        |   `image`             |
  
        | List field                   |
        `{fieldName}/{index}`                                                      
        | `images/2`            |
  
        | Field in micronode field     |
        `{micronodeFieldName}/{fieldName}`                                   
        | `header/image`        |
  
        | Field in micronode list      |
        `{micronodeFieldName}/{micronodeIndex}/{fieldName}`                  
        |   `contents/1/image`  |
  
        | Field list in micronode      |
        `{micronodeFieldName}/{fieldName}/{fieldIndex}`                
        |  `content/images/3`   |
  
        | Field list in micronode list |
        `{micronodeFieldName}/{micronodeIndex}/{fieldName}/{fieldIndex}`
        | `contents/2/images/1` |
      required: true
      schema:
        type: string

Use https://editor.swagger.io/ and insert the above specification to view the documentation.
Webroot requests to list items or binaries in micronodes are not possible.

Additionally, the binary uuid should be exposed in the node response to allow for removing or reordering binaries in a list, similar to micronode lists.

[philippguertler]

Tasks:

• Implementation (BinaryListField, API, exposing binary uuids, deleting/reordering binaries in lists)
• Elasticsearch
• GraphQL (Binary uuid, BinaryListField type, fetching binaries in micronodes)
• Documentation
• MeshRestClient
• Tests

[Jotschi]

Maybe it would be easier and more consistent to use a dedicated endpoint to CRUD binary data. This way we would not clutter and over-complicate the current node API.