core (memory/encryption): set encrypted flag also for outgoing messages and put it in extra: - `encrypted` flag is now put directly in extra, so that there is nothing to change when sending the message to bridge for frontends to be aware of it. - this flag is now also set when markAsEncrypted is used, so frontend can display appropriate indicator to show that outgoing message is encrypted or not.

# 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()