Initial additional layout support for non-ASCII layouts

[LordTermor]

No description provided.

[adriaandegroot]

Merged, thank you! I have a fix-keyboardq branch that uses all the new Config bits -- it is actually more about fixing the keyboard module, and I can tell that the right files are written with improved layouts already -- which will land shortly and bring in your work for the next release.

Looking at the code afterwards for style and improvements, I was wondering about this one:

 static AdditionalLayoutInfo getAdditionalLayoutInfo( const QString& layout );

That looks like it could be a constructor of AdditionalLayoutInfo (although then it would also need a default constructor, I think) and then the documentation for what that represents can move to the AdditionalLayoutInfo header.