android pre-populated databases; support deleting databases on API < 16

Working on issue #10 -- Android part ready for review.  Tested on Android emulator for 4.4 (API 19) and 2.3 (API 10).  Also implemented deleting databases on Android API < 16 from discussion in #86.

This is my first experience with Android as well as my first pull request; critiques encouraged.
Won't this destroy and re-create the database every time the user opens the app? Instead, I would recommend setting a local Preference so you can know whether or not the pre-population has already occurred.  I.e.:

```
// log the fact that we're already pre-populated
SharedPreferences sharedPrefs = PreferenceManager.getSharedPreferences("sqlitePlugin.xml", Context.MODE_PRIVATE);
Editor editor = sharedPrefs.edit();
editor.putBoolean("prepopulated", true);
editor.commit();

// check if we're prepopulated
boolean alreadyPrepopulated = sharedPrefs.getBoolean("prepopulated", false);
```