Issue #30 - Finish the survey activity after submit

* Avoid the automatic creating of respondents.
Issue #28 - Refactor database upgrade

* Legacy DB upgrades clean up.
* New upgrade model (cascading update)
* Use uppercase keywords on SQL statements
* Remove unnecessary code (pref checks, context ref)
Issue #28 - Add surveyal time to zip file

* Add survey respondent start time to the database
* Append surveyal time to data.txt (last column)
Issue #28 - Add upgrade method description
Merge branch 'feature/timing' into develop