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.
However it appears closed to every thread that calls close on the AndroidSQLite object even when the db is actually still open.
For JavaSE behaviour is unchanged. Each thread closes connection to the db
IndexManagerIndexTest now uses datastore.close() to close the db
Merge pull request #38 from cloudant/34308_close_sqlite_connections

Correctly close SQLite Database