Invitation button for activities (only for admins).
Filling the compose form with predefined texts. (selecting the group does not work yet)
Now the message has a markdown element, and the transformation to HTML is only done in the mailsenderAPI.
sending mails from here and there
Message now has a HTML-Addon field which is appended to the markdown text.
Message now contains a button that can be used to register for the activity.
Added headings to some message body parts.
Merge remote-tracking branch 'upstream/master'

Conflicts:
	lib/activities/views/get.jade
Fixed jshint issues.
Merge pull request #215 from NicoleRauch/master

Mailversand