Pages: added url_cache setting: when url_cache is set, result of parse_url is cached (per profile, because in some pages date retrieved may differ between profiles), and then reused. This is useful if some data are fetched during parse_url (e.g. bridge/XMPP call).

try:
    from common.constants import Const as C
except ImportError:
    pass # import doesn't work at this stage with pyjamas
else:
    __version__ = C.APP_VERSION