add an url-param to bypass or refresh a cached route's result

[dersphere]

Like discussed on IRC.

Example:

/cached_route/?refresh_cache=true
/cached_route/?bypass_cache=true

Which would result in

@plugin.cached_route('/cached_route/', TTL=600)
def get_foo():
    return api.get_stuff()

returning fresh data, even when TTL is not reached.