fix some nasty image cache issues i've found like double-frees, leaks

fix some nasty image cache issues i've found like double-frees, leaks
etc. etc. in corner-cases. it also re-factors the image cache code to
be much more manageable and understandable with cache/list management
doing the right thing in the internal calls.

git-svn-id: svn+ssh://svn.enlightenment.org/var/svn/e/trunk/evas@58779 7cbeb6ba-43b4-40fd-8cce-4c39aea84d33