Attention: This is commit has bugs! There is a Segfault in Menu functionality

Cleaned up Pictures menu
Fixed indent in libAfterStep and src/afterstep
Added functionality to download previes from web for web backgrounds - untested!
Minor tweaks to libAfterImage/Makefile to not rebuild for no reason
Moved -Wall to --enable-warn
Added -w to --enable-gdb
Other minor tweaks.