Rename the Compiz project to Opal

See the title.

This is specifically for my fork of the  Compiz project and not anything else.

compiz -> opal

compiz-plugins-main -> opal-plugins-main

compiz-plugins-extra -> opal-plugins-extra (merge with opal-plugins-main?) 

compiz-plugins-unsupported -> opal-plugins-unsupported (merge with opal-plugins-main?)

emerald -> anahi