Support repeatable form elements

[vinayvenu]

Acceptance criteria

• When there is a repeatable question group form element, then it should be possible to add new items into it
• It should be possible to disable manual addition and removal on the repeatable question group
• Rules for visibility, values showAnswers etc should work on repeatable question groups

[mahalakshme]

As part of avniproject/avni-models#43, support of question group and repeatable question group is done for execution of rules in server(code changes in avni-server and rules-server codebase). Try to unify the code in a single place to make it work in webapp. Else when a new concept is introduced, changes to support it, need to be done in 3 places: API support, webapp support, server rules execution support(this is the current situation).

Reference issue related to this: avniproject/avni-models#47