Add activity to handle default dialer requests

* ChangeDefaultDialerDialog provides the UI that can be used by
apps to request that the user select their package as the default
dialer.

* Add various manifest entries, strings etc for use in the UI

* Exercise TelecomManager.ACTION_CHANGE_DEFAULT_DIALER in
TestDialerActivity

Bug: 20304411

Change-Id: Ibc6678c44290f5c9aa00c294b55db74c2c6e09eb
4 files changed