baobab: Make DBus-activatable

This commit installs a service file, renames the desktop file
to follow the bus name, and adds the DBusActivatable key to the
desktop file, following
https://wiki.gnome.org/HowDoI/DBusApplicationLaunching

https://bugzilla.gnome.org/show_bug.cgi?id=727918
Guard against null strings before escaping
Disable chart switcher while in the busy state