Better icon for qgit

Hi, Marco!

I see that qgit got its own icon, but I think it's confusing to reuse an icon used by another project. I'm attaching what I think would be a better qgit icon. I tried to use the same gamma but represent the unique qgit look.

I understand that only one icon can be used, and it should better be a 16x16 icon to avoid scaling.

I'm copying the git list in case somebody could improve the icon or suggest something better.