More support for inverted CM11 themes

Since the switch to MMS-caf, as it uses some fixed colors, many CM11 themes that has inverted the app (holo dark theme) aren't looking fine. Let's make it more themeable.

Change-Id: I99a4d6762aafa8175abefca07287e5e2b7484448
Reuse @style/MmsHoloTheme in sub-activities

By using @style/MmsHoloTheme in sub-activities (like 'Setting') instead of
inheriting from @android there will be more consistency around the app
if a theme developer modifies the main theme (e.g. when inverting the app
colors).

Change-Id: I92851cbe8375d995067e515d2dabdf6d9225a7e5
Mms: Remove SMS signature summary

Change-Id: Ic0be25fffda3ebc64fbaa7becd8e0d0064fcfe2f
Mms: Improve some strings

Change-Id: Ibe19e5f685e44a2c54d6331ca7b5483bedfa7310
Merge branch into kk_mkt