Changed musicbrainzws2-java library to returned dates fetched from MusicBrainz as UTC timestamp instead of local.

SimpleDateFormat uses TimeZone.getDefault() as timezone when parsing from string dates to java.util.Date.
Force a re-initialization of database field release.dateRelease, which was filled by musicbrainz libary with local timestamps instead of UTC
Adapted database to not overwrite creation date of artists and release and show only releases with a release date.

This was necessary after rev. 4d6c306dee336e45bb8803f9240affc56560fa21, as we don't want to show releases without a release date and don't want to show all existing releases as "just added" again.
Fixed possilbe NPE introduced in re. 98ae55f
Fixed another possible NPE introduced in rev. 98ae55f0c00c2140fd805131f422d90feeebd978
Implemented tabs Available and Announced
Adapted dates displayed on release list to show dates as UTC (instead of local dates) after changes in rev. 734bdf10b234dd3fd186b71bf96b5dbb586776a
Example: Release Date is 2014-07-14 00:00:00. Interpreting the this as GMT-1 would display 2014-07-13 as release date.
Merge branch 'feature/AvailableAnnouncedTabs' into develop
Moved maven android dependency in a separate "non-eclipse" profile in order for eclipse to not screw up dexing when starting the app
Optimized build
Prepared new version
Merge branch 'release/0.6'