adb: Improve ADB's forward redirection management.

This adds a few new options/modes to 'adb forward':

  adb forward --list
  adb forward --remove <local>
  adb forward --remove-all
  adb forward --no-rebind <local> <remote>

For more context, see http://code.google.com/p/android/issues/detail?id=39631

Note that this only affects the host adb client and server programs,
i.e. it's compatible with devices running older adbd versions.

Change-Id: I9cda3ba12b5a8560a2061620bc7f948e5c1e70f7