ME: added 'field_xpath' field in attachment serializer
ME: refactored test; added missing field
ME: added a check for filename in list
ME: refactored 'get_field_xpath' method
ME: refactored implementation of get_field_xpath function
ME: refactored 'get_field_xpath' to use a recursive function
ME: made code more clean
ME: refactored 'get_path' to allow finding of nodes that are nested
ME: abstracted functionality for getting key by value in a dict
ME: refactored 'get_field_xpath'; moved recursive function outside class
ME: a test for 'get_path' function
Merge pull request #672 from onaio/559-make-media-API-more-consumer-friendly

559 make media api more consumer friendly
DW: Added version to xform and instance. Overide the default partial update to replace a form
DW: Corrected failing tests
DW: Added test for a bad xls file update. added version param in data export and code refactor
DW: Code refactor
DW: Added more tests, removed the seconds in the version, code refactor
DW: Code refactor
DW: Corrected failing tests