Add Signature to messages

This adds a custom signature option to Mms app,
which appends a custom string set in settings
to all messages send.

PS2 : Fix Test Derp

Credits: DroidJunk

Change-Id: I2b3572e47a183c18c70bf8ef4960d60695ac3c4b
Add Easy Selector

When creating a new message you have to write some letters from the
contacts you want to add and select them by clicking on it.
This can be annoying if you want to send your message to several contacts.
With this change you can manually select numbers from contacts from a
checkbox list.

PS 2 : Fix NPE

NOTE: Full credits to Eric Mourougandy <emourougandy@gmail.com>

Change-Id: I94c130bd40ec5dc872446ce66c57a4eb146553af

Conflicts:

	res/values/strings.xml