standardize data sent through websocket and CollabStats

[valerino]

all of the data sent through the websocket and the stats on the collab database should have, at least,

• operation_id (or operation name is better ?)
• client_id (or client name is better ?)
• username (and/or user_id ?)

this is for a future administration console to correctly display who does what and in which context (operation).

also relates to #6 and #10

[valerino]

20