core (memory/persistent): implemented `aset` and `adel`: those methods are async variants of __setitem__ and __delitem__, they return a Deferred fired when the value is actually set/removed from storage.

# 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()