ConfigParams::SolutionFile should not be a glob

[awseward]

The name SolutionFile in ConfigParams implies a singlular file, and so the fact that it is actually a string seq is pretty confusing.

We need to decide whether we want to support building project with multiple sln files (what does that even mean...) or just change SolutionFile to be just a string.

My vote is for the latter, but I'd like to hear if you feel otherwise, @mglodack.