Rework package and class layout

[AntonOellerer]

Currently, the package and class layout does not really follow a structured layout (Top-level package, impl package where all implementations are, annotations package only important for the reflection resolver directly in the root package.

This makes it very hard to understand the broader layout of this library from just looking at the class names.

The package and class layout should be redone to better reflect responsibilities (e.g. a resolver and a document package ...)