save session id in redis

[njustus]

.. and not in memory. The SessionService is already stateless so no need to save the reference.

Not only save the session id, save the mope endpoint address too.. So there is no need for a name service (#67) because the address is already known:

save at webmodelica::sessions::1234-5678-78901

id: 1234-5678-78901
project-id: 98
project-path: http://mope-service-1:9020/mope/project/98

[njustus]

When the session is saved into redis.. document it somewhere ..