Ported monster tank madness to lua

It would be nice, if someone could already have a look at this (style nits?),
although this is not completely finished yet (see todo).

[This](https://github.com/abcdefg30/OpenRA/compare/monstertankmadness?expand=1#diff-da0b70bbc22b6b4af2fbe96dd5c5a8b7R18) set to true can help testing.