[#193] Fetch and display username

* Remove unused Bundle attributes
[#193] Clean up

* Simplify loader callbacks (no need for ID with a single loader)
[#193] Add submitter column

* Add db column, handling db upgrades in the fall-though approach
[#193] Read SurveyInstance.SUBMITTER

* If available, display submitter
[#193] Parse and store submitter

* Read optional json attribute
* Store submitter in survey instance table
Merge pull request #203 from akvo/issue/193-form-user

Issue/193 form user