LCD Density changer ported from slim to AOKP (AICP)

PS1: - Initial commit
     - DensityChanger.java: ported SU commands to AOKP
     - DensityChanger.java: added necessary imports
     - DensityChanger.java: more i probably forgot

     - original commit so i know what i did later:
       https://github.com/CarbonDev/android_packages_apps_CarbonFibers/commit/5caf16a99ea724aa2aad605ad4f4a8e212b6b625

      - Working: everything except playstore stuff which will be removed anyway

      - ToDo: - XML -> remove summary
              - Playstore Stuff -> remove
              - Popup Message after changing DPI should say that usage of
                a  MultiDPI Playstore is recommended instead of actual message
              - New Icon for LCD Density needed
PS2:
      - bring in icons for xhdpi, hdpi, mdpi
      - remove double entry for RC - General UI - LCD Density
      - remove market stuff and just keep stock density, custom and reboot

ToDo:
      - change all dialogs
      - maybe bring in a tab with hacked playstore and on click
        u can download a hacked playstore
      - cleanup

PS3:
      - changed dialoges
      - LCD density is now LCD Density to fit in RC menu
      - xml cleanup but not finished yet

Change-Id: I79d466c8289648eff1af691789897e1ba2ef80d5