Splaspage: Add highlights. Fix cfp inclusion.

https://github.com/openSUSE/osem/issues/544
https://github.com/openSUSE/osem/issues/545

@hennevogel perhaps some ideas for styling? :)
Hm, I'm right that you just drop the 'Keynote' event type from the dropdown so that the user can't select it anymore?
I think we have to check this in the controller / model too because otherwise the user could simply POST/PUT 'keynote' anyway...
@hennevogel What do you think?