Created pnd_desktop.[ch] pair, to contain relocated dotdesktop and icon stuff

Created pnd_desktop.[ch] pair, to contain relocated dotdesktop and icon stuff
Relocated hup-script config key/default to pnd_desktop
Figured that app searchpath was being misused -- using for both app searchpath and notify searchpath, so
created new config entry for notify searchpath; ie: you might wish to notify on /media so that dirs
created by automount will be detected, but you may not wish to find .pnd files in that path (since it
recurses and would thus find apps on the entire SD card.)