Rewrites checkVersion and checkVersionNewer in utils-service.js, refines upgradeToVersion

- Adds unit tests that cover all cases.
- Adds call to parseVersionString() so we can pass it version string e.g. '1.0.1'
- persistence-service.js now also manages JamstashVersion. It is set in localStorage from app.js's constant, and not from the changelog so we don't have to add a version to the changelog to actually do stuff.
- persistence-service.js's upgradeToVersion() now only applies newer changesets. This ensures we won't erase users' settings with changesets at every new version, e.g. resetting songSearchType to song every time.
- upgradeToVersion() will also notify the user of the upgrade, which was formerly done in settings.js

app/app.js

@@ -50,5 +50,5 @@ angular.module('JamStash', ['ngCookies', 'ngRoute', 'ngSanitize', 'ui.keypress',
     }]);
 }])
 
-//TODO: store as version object
+//TODO: Hyz: Fill with grunt task
 .constant('jamstashVersion', '4.4.5');