Move some non-themed icons to pixmaps/ directory

* Add PIXMAP_PATH to constants
* Add PIXMAP_PATH to icon search path in Functions.py
* Add data/icons/pixmaps/ directory
* Move some icons to $datadir/pixmaps/blueman/
* Add pixmaps stuff to configure.ac
Merge pull request #132 from rworkman/pixmap_move-review

Move some non-themed icons to pixmaps/ directory

I'm fine with things as is, you can file another pull if you want to adjust this in the future