New APN database

## apntool
* Imports Google-provided apns xml file (found in Android and Hangouts app)
* Creates a gzipped easily-queried, legacy-friendly SQLite database
* `./gradlew -q updateApnDatabase` to re-run and copy over the new asset

## ApnDatabase
* Use SQLiteAssetHelper to gunzip from assets and version control the database
    * DB version is set to Google's xml file version for easily tracking when we need to update
* Lookup MMSC info with the following priorities:
    1. Try to get relevant MCC+MNC from multiple places in order of probability of it being correct
    2. If MCC+MNC was available, also try to get APN name via the MMS `NetworkInfo`'s `extraInfo` string.
    3. If no matching MMSCs were found including APN name, try without the APN (old behavior)
Thought it would be nice to not have the Database class have logic on dealing with the underlying files holding the DB, since that's what SQLiteOpenHelper was there to abstract out. Think I should I ditch the helper anyway?