[cleanup] style fixes, add nodes, 0.2 cents refactorings

[undo] during undoing, call hooks in the [active]integrity and undo categories

[repo] refactor fti operation to use set_operation and a single operation whatever the number of entities to ft index

[querier] introduce RepeatList class, used to optimize size of data returned for result set description When rql query has no ambiguity, we used to return the same description * N where N is the size of the result set. Returning RepeatList class avoid that multiplication. According to quick benchmark this improve performance for result set whose size is ~ > 50, has very small penalty for rset < 50, and in any case improve the size of data to be transfered over the network through pyro connection.

[repo] on add entity, set cache as soon as possible + fill type/source cache

[repo] more efficient eid cache operations handling based on set_operation; refactor * split CleanupEidTypeCache operation into one operation for deleted eids and another for added eids, and put them in cw.server.hook * for consistency, move fti unindexing handling from the repository to the system source * handling of deleted eids is done in plan execution (ssplanner), no needs to redo it in *delete_info -> no more need for _prepare_delete_info method, killed

[repo] move eschema_eid function from hooks.metadata to server.utils

[primary view] skip virtual rtypes anyway

[test] CubicWebTC.create_user expect an actual query, and we don't need to give session here

[dataimport] stop disabling undo ; commit return transaction id