routes: Actually match metadata when finding routes, fix problems with paths. When we look for a route that matches a given page, we now look at the source metadata that comes with that page, and compare it to the metadata we need to build URIs. Also, when matching URIs, we handle the case where a 'path'-component in our pattern may be completely empty, and thus we may be missing some trailing slashes in the URI.

PRIORITY_FIRST = -1
PRIORITY_NORMAL = 0
PRIORITY_LAST = 1


class Formatter(object):
    FORMAT_NAMES = None
    OUTPUT_FORMAT = None

    def __init__(self):
        self.priority = PRIORITY_NORMAL

    def initialize(self, app):
        self.app = app

    def render(self, format_name, txt):
        raise NotImplementedError()