Null no no... (Preemptively react to DI changes)

DI has been returning/proving null for services that are not registered. This is about to change. Updating EF to depend on IEnumerables for optional services and to not expect GetService to return null.
SQLite: Add some low-hanging fruit implementation

Changes include:
* Fix CreateTables & HasTables on SQLiteDataStoreCreator
* Implement SQLiteDataStoreCreator.Delete
* Update SQLiteTypeMapper.GetTypeMapping to use aspnet/DataCommon.SQLite#32