UK: get id_string from data/instance
UK: use pyxform branch with xform2json updates, allows most xforms to be uploaded by briefcase
UK: pin down jsonfield to version lass than 1.0
Merge pull request #528 from onaio/pyxform-briefcase-upload-issues

allow briefcase to upload xforms and submissions
ME: included 'created_by' property in projects endpoint
ME: added a check for 'created_by' in 'test_projects_list' test case
ME: removed 'created_by' check to see if the test will still fail on travis
ME: added 'created_by' to excluded properties in project_serializer.py
ME: reverted to earlier changes; removed created_by from exclude property and added an assert in test_projects_list