added a dock widget to show a list of molecules
reorganized main() to process input with or without GUI

* always create an instance of molconv_window to process the
  molecule file(s) that are read. The GUI is started optionally.
* added a function to save the first molecule that is read in to 
  an output file.
* ISSUE: The cleanup function does not work at the moment.
Merge remote-tracking branch 'origin/cmake_chemkit' into cmake_chemkit

Conflicts:
	source/molconv.cpp