DW: returns a json response on error
DW: Added a check for a template before report generation, updated the documentation on xls reports, updated and added tests
DW: Concatinating string using format instead of using +
Merge pull request #694 from onaio/690_return_json_object_in_xls_report

Checks for a external export template
DW:ME Made the close icon working and annonymous users cannot view the edit and delete button
ME: updated tests to check for 'Last-Modified' Header property
ME: added 'Last-Modified' Header property to the viewsets
ME: added functions to get formatted header date and to get date based on args
ME: fixed bug causing incorrect field_xpath and updated test
fixed 'NoneType' error causes by connect and user_profile viewsets
ME: refactored 'get_date' and added 'last_modified_header' and 'merge_dicts' functions
ME: refactored code; implemented 'last_modified_header', 'get_date' and 'merge_dicts' functions is viewsets
Merge pull request #696 from onaio/619-enable-last-modified-header-on-api-outputs

619 enable last modified header on api outputs
Merge pull request #697 from onaio/682_edit_delete_button_shows_up_for_non_signed_users

DW:ME Made the close icon work and anonymous users cannot view the e...
UK: Project and ProjectXForm in logger
UK: migrate data from api_project to logger project
UK: add project field to xform
UK: change Project imports

Conflicts:
	onadata/libs/serializers/project_serializer.py
UK: remove api.Project and api.ProjectXForm
UK: update projectxform relation to px_xforms relation, create_default_project also sets the xform.project