Pattern-based subscriptions and Pattern class

Pattern.match() should also match strings like ``foo..abc..deforfoo.abc.` for patterns like `foo..abc.arg2:int.def` and `foo.abc.` repsectively and return `None` for the missing fields.

Usecase: Custom authorizators in crossbar currently get strings like above as input if prefix or wildcard subscriptions are used. Pattern should be able to deal with any string labeled as "uri" or crossbar has to change behaviour.

Start at the Pattern.match() entry point and trace how pattern-based subscriptions parse URI strings; the issue does not name a file or test. Compare the two provided input examples with their patterns, including missing fields, and verify that matching returns None for each absent field without changing other subscription behavior.