Improve command line interface including example

[dpizetta]

Some options to include, some already have:

example (present just dark) example --no-dark (present only no dark) example --each (present each one, dark and no dark, interleaved) example --both (present both, dark and no dark, open two windows) example --recompile (recompile all, example ui and qdarkstyle rc files) example --loop (when closed, proceed everything configured again, nice when developing)