Disable Baloo indexing on mountpoints for KDE users

[jstaf]

Enough users have run into trouble with KDE's Baloo file indexer trying to index their entire mountpoint that it might be a good idea to automatically add mountpoints to the list of Baloo's excluded folders.

(There needs to be a way to disable this though in settings somewhere... and we don't even support settings/configuration right now, so this may need to wait until we get there.)