Rename 'unresolved' to 'routing' module

The latter will reflect the fact this module will soon be handling
aliased routes.
ApiRoute class

Extends the webapp2 Route class, specifically adding the ability to pass
a list of route template aliases with the constructor.
Integrate ApiRoute with application initialization

Promotes all the existing routes to be full-fledged ApiRoutes instances
and specify lists of aliases, except for the catch-all route.
Allow separate specification of unresolved handler

This will make it easier for the application constructor to intermingle
the alias routes between the regular routes and the "not found" route in
the future.
Implement alias redirects

Introduces a new handler, refines the existing redirect reasons in the
statistics implementation.
Additional aliases

Adds /api/version as an alias to /api.
Allow alias redirects with parameters

This is really as simple as passing along the arguments from the alias
route to the official route. For the mapping to work, the former needs
to just support as many arguments as the latter.
Alias consolidation

With the new passing rules, we can actually condense these using unnamed
regular expression parameters (since extra parameters in the alias
routes will not affect the built official route).
Merge branch 'topic/web-api.aliases'

Brings the alias functionality in the main topic branch.