[examples] Add a basic Qt GUI
[examples] Add a .pro to ease development of an out-of-tree GUI

Tested on Linux & Windows. Mac will probably need some fixes...
[examples] Move test-medulla and add 3 lines of doc
[examples] Add a short readme
[examples] Move clients to their own directory
Merge pull request #199 from vaussard/add-examples-rebase

Thank you very much!