Added support for a hup script; if the pnd.hupscript key is within the 'apps' config...

Added support for a hup script; if the pnd.hupscript key is within the 'apps' config, then after emitting .desktop files pndnotifyd will attempt to invoke the
hupscript, which could in turn hup the launcher application (to let it know to rescan)

Fiddled with re-setting-up-notifiers after autodiscovery (to handle newly mounted directories, in case user downloads an app on-device, or uses the shell, etc),
but led to some odd situations. (ie: shutting down and reopening the inotify fd seemed to cause it to immediately need a rescan, so could repeat 2 or 3 times..)