plugin 0249: fixed invitation handling + some improvments: - properly retrieve payload by namespace - now use a trigger instead of observer, so the message workflow is stopped if an invitation is found - namespace is registered fix 241

# XXX: the Monkey Patch is here and not in src/__init__ to avoir issues with pyjamas compilation
# TODO: remove this when changes are merged in Wokkel
from sat_tmp.wokkel import install
install()