Create gamemode to ease map testing at mapeditor

[reaby]

It should have minimal/default ruleset and markers for bases and flag.
When flag is picked up, apply handicaps: Fragile and 0.8 acceleration.

[Geekid812]

We should probably have the libs refactored before working on a test version for the gamemode. We could then use the TeamFlagModeBase.Script.txt to more easily derive from the main gamemode. It would also mean some part of the code would be open-source, but I'm not against it.

[Ze-Rax]

Markers don't work in local play (that is "Test with mode" or in the map editor directly)

Also, isn't there a way to include a basic rule set in the maptype itself, so when you press enter and place the car in the map, you can just test it with this minimal ruleset?

Then we wouldn't need another partial mode, that could become pretty messy to implement.