Implement missing classes for the build to succeed.

Several classes are missing from the framework and intented to be
created by the myriad-assistant tool. In order to get a standalone
myriad generator (for all cases) these classes need be implemented and
compiled in advance. With this commit the basic stub of the missing
classes was added. Additionally a rudimentary main class was
implemented. The build now produces an executable binary..
Fix and clean CMakeLists files.

Module names were changed to CamelCase notation, header files were
explicitly listed, custom targets create, an executable added and
linked.
Implement Main, GeneratorConfig, and GeneratorSubsystem
Fix wrong string concatenation.