Optimized suffix checking.

Suffix checking easier and more efficient.

I also fixed some unittests some others that triggered, I disabled (Soenke please review).

My next pull request will most likely fix the hard coded location of app.d found in some places. I would also use the opportunity and make it configurable via an appFile setting.
So afterwards it will use appFile (if defined, platform specific suffix will be supported), if none is specified it will use app.d or projectName.d when found, just as it does now. Would this be ok? Is the name appFile ok?