add map test-navcons

[sweet235]

This map by @cu-kai is in the public domain. Its purpose is to test Unvanquished/unvanquished-mapeditor-support#22

[cu-kai]

I had some vision that this repository required the built / packaged map too but I guess I was wrong. Thanks for doing this.

[sweet235]

We do not yet have support for the navcon entities in this map. But we do have a prototype program that will read this map and output navcon files, at https://github.com/sweet235/navcon-extractor. That is how the navcon files in map-test-navcons_*.dpk were generated.

[illwieckz]

I merged after having denumberized the map.

You can configure NetRadiant to not write noisy comments mentionning every brush and entity number in Preferences → Settings → [ ] Add entity and brush number comments on map write (disable). This save spaces and makes diff easier (so it's more git-friendly that way). 😉️