Ship::UseEcm() return result to Lua

Continuation of #3092, now it returns two statements, as described in `LuaShip.cpp`

![UseECM](https://cloud.githubusercontent.com/assets/619390/3752040/31de5a3e-1804-11e4-902d-ae0aada3db9b.png)

This is the best I could do. I don't think it's possible to use lambda functions in `sigc::mem_fun()`, at least that's my understanding of a stackoverflow post, so had to introduce a second function which returned void.