Merge branch 'mirceakitsune/campaign_gametype_icon' into 'master'

Draw the gametype icon on campaign entries

Since I've been doing multiple campaign fixes, I decided to include an update to the menu part as well. I wanted to see how it would look if the gametype icon of levels was also displayed within the field. Personally I find it good looking, as well somewhat easier to tell which level you're at with this change.

I tried several combinations; Above the checkmark looked okay, but it's harder to tell which level the icon is referring to... it seems to look best on the right side of the map preview image. I included a few screenshots, the first representing the old appearance and the last being what the MR currently adds... if you find another position better please suggest it and I'll make a new commit.

![campaign](/uploads/3cf11cc059b9353dfa1dc973c4e859b9/campaign.jpg)
![campaign_above_checkmark](/uploads/9537d4e2bc7919f4275c8848ffbba405/campaign_above_checkmark.jpg)
![campaign_preview_left](/uploads/2ecd0dfa12246c26a9accc4485658b4e/campaign_preview_left.jpg)
![campaign_preview_right](/uploads/f4b32394f3b54e13daf43a50e32b33a7/campaign_preview_right.jpg)

See merge request xonotic/xonotic-data.pk3dir!748