Added a trivial Android app
Added database contract & helper; test project

Test project contains a pair of fairly trivial tests. The database
helper's test in particular is (virtually) unnecessary: it only checks
the helper returns approximately the expected database.
Enforce FK, tag uniqueness; rename some classes
Refactor: rename project/tests
Merge pull request #1 from patrick-conley/244-database-to-store-track-metadata

244 database to store track metadata