3.0: Make console option parsers mergable/combinable

Resolves https://github.com/cakephp/cakephp/issues/5231

Make console option parsers mergable/combinable
The merging must assume that the args don't change and that the parsers are compatible in this way. It is mainly about the options.
What would you propose? That we use the one with the "most" arguments as it is the one with the most likely complete argument list? That would probably be even smarter.