TouchGFXConfiguration.cpp breaks if no header declares using namespace touchgfx

Our coding guideline discourages the use of using-directives. This is pretty common, I think. I'm removing them from the headers where I can, i.e. from code that does not get regenerated on every code generation in TouchGFX Designer.

I am able to break TouchGFXConfiguration.cpp by removing all using touchgfx declarations from its dependency tree.

I have 2 suggestions:

1. Add namespace references to TouchGFXConfiguration.cpp
2. Maybe remove using-directives from all the headers. There's now a confusing mix, some headers have them, some don't.