Add "Default tab" setting to pick the tab opened when launching the

Phone app.

Choices are:
 * Last used to make a call (Default) - the current behavior
 * Last viewed - this isn't persistent, but usable enough
 * Phone
 * Call log
 * Contacts
 * Favorites

Handles issue 3139
http://code.google.com/p/cyanogenmod/issues/detail?id=3139

Change-Id: I1446850c5f82df05a8888534f7d5de6c30c6ec57