Consolidated wsgi() factory

Merges the Node, Branch, and Capture classes' dynamic(), max_str(),
max_nodes(), and wsgi() into a single wsgi() method. This has the
benefit of reducing overall code footprint, but also means that when a
caller asks for a WSGI callable, we only have to walk the data structure
once and we do not end up with an intermediate throwaway structure.
Removal of Capture's mlen instance variable

This was previously used internally by the class to calculate string
lengths for the captures when calculating max_str(), but its
functionality has been moved into the new consolidated wsgi() method.
Dummy data parameter for Capture's populate()

Because the implementation now uses wsgi()'s maximum string length
calculation rather than setting mlen internally, Capture's populate()
method once again does not use the data parameter (and instead replaces
it when calling the successive node).
Privatize Node and Capture instance variables

Many of these are specific to the implementation and do not need to be
visible by the Locator instance.
Merge branch 'chg/web-api-routing.single-call'

Brings in changes to allow the WSGI callable to be built using only a
single recursive walker instead of several and without generating an
intermediate data structure.