This patch adds a new filter 'msg_urgency' which _matches_ on the urgency on
the notification.
This allows to configure different notification parameters/scripts to different
urgency levels.
Add an option for disabling marking messages containing URLs or actions.
This means that messages will not be displayed with "(U)" or "(A)"
before them, but you can still use the context menu on them.
Put all global variables that store user settings into
a struct to keep the namespace clean. Move loading of
settings into own file so that only the namespace of
settings.c gets polluted with the stuff from config.h