Started integrating functionality into GUI.

- exception.h: added short exception message; fixed what() method; fixed
  THROW_VSC_EXCEPTION in the whole project.
- ConfigParameters.h: added error log file name; added method to read
  config.
- FakeVoltageSource.h: added possibility to make artifitial delay in
  constructor and to throw an exception after it.
- MainWindow.h/cpp/ui: started integrating functionality into GUI.
- VoltageSourceFactory.h/cc: added method GetNames that returns set of
  supported voltage source names.
- main.cpp: loading config and starting MainWindow.
- parameters.cfg: default program configuration.