DW: Added exception handling for doesnot exists exception in project viewset
DW: Checks function in the supported function list
PLD: refactor status function call
PLD: check that method is not none before calling lower
PLD: more descriptive error message
PLD: add field to show xform active status
PLD: remove active, add check_obj decorator
PLD: use wraps add to project serializer
PLD: more check_obj
PLD: revert reversed check
PLD: add downloadable as an updatable field
PLD: update docs to say title is required
Merge pull request #667 from onaio/618_check_stat_function

DW: Checks function in the supported function list
Merge pull request #659 from onaio/590-project-doesnt-exists-error

DW: Added exception handling for doesnot exists exception in project vie...
Merge pull request #657 from onaio/add-active

Use decorator to check for object in serializers
ME: refactored 'retrieve' method to include 'export_handler'
ME: added list action
ME: added a test for data endpoint xls export
ME: added ability to access list action without 'pk' or when pk is 'public'
ME: replaced 'export_handler' with 'custom_response_handler'