add app_id and build_id to forms api (v0.4)

add build_id to the es form index
make app_id and build_id in form API nullable
Merge pull request #3595 from dimagi/form-api-app_id

Add app_id and  build_id to form API
add test for forms where data and ui have different hierarchies
fix bug with forms where data and ui have different hierarchies