Added a beatmap cache database.

- New database ".opsu.db" stores a cached copy of all parsed beatmaps.  All data will be read from this database unless the last modified time of a beatmap file does not match the one in the table.
- OsuParser inserts all new entries to the database in batch after parsing.
- Added *toString()/*fromString() methods for 'breaks', 'timingPoints', and 'combo' fields in OsuFile for use with the database.
- For any database format changes, update the DATABASE_VERSION field in OsuDB.
- Reloading beatmaps (F5) will now clear the beatmap cache.

Related changes:
- Added small DBController class for convenience.
- Changed 'bg' field of OsuFile to only contain the image file name, instead of the full path.
- Deleted printDatabase() method from ScoreDB.

Signed-off-by: Jeffrey Han <itdelatrisu@gmail.com>

.gitignore

@@ -4,6 +4,7 @@
 /Songs/
 /.opsu.log
 /.opsu.cfg
+/.opsu.db
 /.opsu_scores.db
 
 # Eclipse