Very old todo: Packed file UI

- The "ID" buttons (for browse images, for example) now show a Pack icon, for packed
  Images. Using this button allows unpack.

- Pack and unpack operations now give a Info report on what happened.

- Not restored yet: option to set "AutoPack".




git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@54120 954f8c5b-7b00-dc11-b283-0030488c597c