coordination: add option to jump into state-machines

by passing the argument :starting_state the user can choose
states in which a statemachine should start.

These states needs to be dinfed within the statemachine as:

prepare_jumpin("wall" => wall1, "pipeline"=> pipeline1)
This tests two unrelated things:
 - that #optional_arg defines an argument
 - that #has_arg? can handle both symbol and string

It does NOT test that the default is properly handled, though

Split it into two tests.