UK: add,change,delete permissions to user and org profiles for owner
UK: userprofile require_auth=False
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
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