Added ability of engineer settings and added to D2K

I added ability of engineer settings works like Tech Levels. #5986 
![image](https://cloud.githubusercontent.com/assets/7933210/3685025/d5e0af7e-1304-11e4-9264-9bff90e6b6be.png)
But it brokes crates at only D2K.(I don't know it's couse)
http://www.mediafire.com/view/flb7dm77lo0fp2y/exception2.log
I don't know why travis is giving this errors.
OpenRA.Lint(1,1): Error: Buildable actor engineer1 has prereq ~engineer.fromout not provided by anything.
OpenRA.Lint(1,1): Error: Buildable actor engineer2 has prereq ~engineer.enter not provided by anything.
They provided at here.