Add event mode to support missions/campaigns

[Marsychen]

Adding a event mode that would support missions/campaigns would be a great addition to the tool.
My suggestion is
-add a possiblity to sign up for a event and/or even a specific task
-add the possiblity to create pacakges and maybe share some common settings among them (see issue #34)
-add the possiblity to fillout a after action report