WIP: Rework commandline

This pull reqest replaces the cmdline parser with CmdOption. I also started to eliminate System.exit() calls from various places. This makes it easier to run JBake as library. The command line parser is used to populate the configuration. With that configuration an instance of the Main class is created. Calls to it's non-static methods will not call System.exit() but will throw a JBakeException in case of an error.

I removed the printUsage() method from Main, as this is now completely rendered by CmdOption. Please note, that is very easy to provide translated versions of it. If you are interested in it, I could create a German translation for it.

WDYT?