Fix #96 Add EBNF grammar for ROS2 names in self-testing python script

[tkruse]

Prototype for #96. Since last time I extended a bit. Because of the fully-qualified vs. non-fully-qualified, the grammar has grown a bit.

The grammar still does not prevent double underscores, the python script around it can handle that much easier I think.

The script itself does not yet handle maximum name length constraints.