core (constants): fixed flatpak config paths for older versions of flatpak: Older versions of Flatpak don't seem to set FLATPAK_ID, but do set FLATPAK_SANDBOX_DIR, so this is now checked too to detect flatpak.

# 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()