Specified journal mode

Room is designed to choose the journal mode itself if none is specified.
greenDAO's journal mode ("TRUNCATE") will stay for now because the journal mode has influence on the behavior caused by issue #529 [1] and because changing the journal mode complicates the migration further.
This can still be changed later.

*This commit is related to issue #529 [1]*

[1] #529

data/src/main/java/org/cryptomator/data/db/DatabaseModule.kt

@@ -51,6 +51,7 @@ class DatabaseModule {
 			.addMigrations(*migrations) //
 			.addCallback(DatabaseCallback) //
 			.openHelperFactory(DatabaseOpenHelperFactory()) //
+			.setJournalMode(RoomDatabase.JournalMode.TRUNCATE) //
 			.build() //Fails if no migration is found (especially when downgrading)
 			.also { //
 				//Migrations are only triggered once the database is used for the first time.