Issue 6606: CM File Manager will not Remember Selection for "Open With" menu

Issue: http://code.google.com/p/cyanogenmod/issues/detail?id=6606

This patch makes the next changes:

* Make the internal editor exportable. Now it can be treated as another activity and can be mark
  as preferred activity, but only for text/* and some text mime/types. For undefined mime/types
  categories, the internal editor is still used in a non preferred mode (internal editor cannot
  be marked as preferred)
* When the internal editor in a non preferred mode is selected, 'remember' checkbox is hidden.
* Improve preferred activity resolution
* Allow clear a preferred activity on the open with dialog (when 'remember' checkbox is unchecked)
* For better compatibility, the internal editor now ignores the ACTION_EDIT action, so opened
  files are always editables (with the exception of binary files that they are opened always as
  read-only)
* Improved onIntentSelected with better NPE and internal editor checks

Change-Id: Ie42990a6c0ccbdd4bfab6ec23ae27cc808cac7b7