Add a record with 2 fields : tnode and tattr

For now, only Eva parameters are registered.
Removes code manually creating such synchronized states from Eva.

In Ivette, adapts Eva sidebar to these synchronized states (names and data are
now automatically generated, and thus are slightly different from the ones
previously used).

Uses add_hook_on_update to also synchronize when the project library changes
the state.

Also adds a warning from the Frama-C server.