Added custom app starter to rotary lockscreen

added silent<->vibrate<->volume to rotary lock screen
added custom app starter to rotary lock screen. since
  turn left/turn right of middle dimple seamed to short,
  i decided to drag down the whole rotary wheel to activate
  the custom app/activity
modified options to reflect these changes in CMParts. i also
  renamed all involved variables and settings, since the old
  variable names only reflected phone and messaging app
renamed the settings strings to propperly explain the options
added resources for custom app starter icon. i felt using
  messaging icon to start a custom app is not very userfriendly,
  so i added a cm icon instead for hdpi and mdpi
used that cm icon on sliding lockscreen, too
added resources for arrow down. since the other two dimples on
  rotary show arrows hinting the user what to do, i added down
  arrows to do the same for middle dimple

screenshots to see results without compiling:
http://picasaweb.google.com/Dave.Astator/RotaryLockscreenTweaks#

Change-Id: Id11b6ae1b97c2b5e6e53a426888fb4277ebdb0c3