Update ORMDroidApplication for DataBase File visibility

Now enable to choose the database file visibility by adding a `<meta-data android:name="ormdroid.database.visibility" android:value="PRIVATE||WORLD_READABLE||WORLD_WRITEABLE"/>` `PRIVATE` by default
Database Visibility

Always set visibility from Application's meta-data
Merge pull request #32 from ChristopheCVB/patch-2

Update ORMDroidApplication for DataBase File visibility