Add doxygen configuration file and comments

For more info on doxygen, see doxygen.org.
For install in Ubuntu/Debian, run "sudo apt-get install doxygen graphwiz"
Generate source documentation/browser with "doxygen qlcplus.dox" in doxygen/
Remove unused class DMXSlider

Should have been removed in e639f2d
Rename OutputPluginStub to IOPluginStub, as it better expresses the purpose
Refactoring: add InputPatch::isPatched(), OutputPatch::isPatched()
Clean GrandMaster code (remove gm prefixes), add unit tests for GrandMaster
Fix Universe tests - not finished yet
Merge pull request #233 from janosvitok/universes

Universes improvements