Quicksettings: USB Tether tile

courtesy of OmniRom
based on: http://goo.gl/0RfbFy

PS3: add "private ConnectivityManager mCM;" variable
PS4: compiles, not yet tested
PS5: derp forgot to initialize mCM which caused a NPE
(http://developer.android.com/reference/android/net/ConnectivityManager.html)
PS6: fixed some connectivity manager redundancies in qs.java
PS8: make tile temporary, only appears when connected to usb.
PS10: fix conflicts in pa_strings and QuickSettingsModel after recents merges.
      clean up commit message's conflicts.
PS11: Remove unnecessary resources
PS12: Don't show tether tile is feature is not supported

Signed-off-by: Andre Saddler <dresadd09691@gmail.com>
Change-Id: I856f1a1f954544cb9e1b78f504fde8916b94235e