icon 6.x-1.0-alpha3

As the previous alpha had some mysterious bugs caused by non-optimal coding, I decided to rewrite parts of the code. At the same time, I reamped much of the code, splitting some functions into smaller ones, generally adding more structure to the module and how it handles icon sets and icons.

Also reamped the iconset selection form to have it look more like the Blocks form. Note that icon sets are not meant to be moved across the different sections - this is something to be fixed!

And, the form's theme function has been replaced by a icon-iconsets-form.tpl.php file.