Optimized and improved logo SVGs and PNGs.

I have optimized the SVGs - they no longer use more than 15kB of redundant data each, and are now all friendly paths and therefore renderable in browsers. The shadow of the Hexchat logo is also no longer cut off to the right. Tray icons, program icons, and miscellaneous PNGs have all been updated to reflect these changes. 

`hexchat-b.svg` doesn't seem to be used anywhere and should probably be removed, but I am not going to make that call.

I almost wanted to remove the RDF data just for size reasons, but I doubt people would like that very much - one thing I noticed and am wondering though - does Peter Zelezny really own the rights to the Hexchat logo?