Rework association names. drop parent_ and child_

[jcoyne]

child_collections  -> collections
parent_collections -> in_collections
child_works -> works
parent_works -> in_works

[elrayle]

Also effected...

• pcdm_behavior.rb#parents -> #is_member_of
• pcdm_behavior.rb#parent_collection_ids -> #in_collection_ids

NOTE: no method for...

• object_behavior.rb#parent_objects_ids

NOTE: Adding deprecation messages for change methods to avoid problems with apps using these methods. Deprecation end date 10-31-2015.

[elrayle]

Rubocop doesn't like #is_member_of. Changed it to #member_of