Correctly close SQLite Database

- In the android SQLite database wrapper the close method only closes when the thread calling close is the thread that created the database.
- For JavaSE behaviour is unchanged. Each thread closes connection to the db
- IndexManagerIndexTest now uses datastore.close() to close the db
Can you provide a few comments for you changes to this class? Particularly here, and possibly in the java se counterpoint class, explaining why the user has to close every threadlocal connection from its own thread.