[migration/3.18] protect against attributes in db missing from fsschema Happens if a previous migration forgot a drop_attribute. Closes #3471609

[doc] Update copyright date to 2014 (closes #3463136)

[repoapi] Fix typos in doc strings and comments

[cwxml parser] minor pylint fixes

[devtools] make CubicWebTC.login as admin undo previous logins Fixes things when login is not used as a context manager.

[devtools] fix self.session._cnx vs self.cnx._cnx confusion after self.login Make sure the client connection and the session refer to the same server connection.

[devtools] _orig_cnx does not exist any more (missing change)

[c-c schema] option to show single etype (closes #3404831)

[multi-sources-removal] Drop entities.source column Since we remove federated multi-sources support, the same value ('system') is always stored in this column and so could be removed. Also, cleanup repository caches and a few api where the very same useless information could be removed. Closes #2919300, at last [jcr: restore sanity check of etype against schema in checkintegrity.has_eid]

[repo] pylint cleanup, mainly of imports, with a bit of style

[multi-sources-removal] Drop no more used federated ('true') multi-sources related code Related to #2919300 (almost done!)

[multi-sources-removal] Turn ConnectionsSet into simpler ConnectionWrapper also, SqliteConnectionWrapper becomes a subclass. This is allowed since now ConnectionsSet responsability has been reduced to handling the system source only. This changeset also: * drops useless cnxset_set / check_connection api * deprecates former .source / .connection / container api but it renames neither the session's cnxset attribute, nor the related repository method. Related to #2919300

[multi-sources-removal] Drop cnxset_freed from source interface Though a hack is still needed when using sqlite Related to #2919300

[cnxset] add backwards compat for cnxset.source_cnxs It's used at least in a vcsfile migration script.