[datafeed cwxml parser] cache processed urls/entities to avoid unnecessary http requests and processing

backport stable

[rql2sql] fix missing sql restriction w/ attribute restriction where value comes from a subquery

[dataimport] fix #1732685: cached entity and shared cw_edited data with NoHookRQLObjectStore

[parsers] fix python2.5 compat problem introduced by 7466:395c966a1cb3

[test] update cubicweb/test/unittest_schema.py (to follow yams#.....)

[server] fix NameError (missing VIRTUAL_RTYPES import) in checkintegrity.py

[schema] fix computing of has_text relation: when a fulltext_container relation is added, we need to recompute has_text for the target entity type as well. Also, avoid computation when not needed

[parsers] remove build_search_rql() that duplicates find_entities()

[vreg] help understanding assertion error

[datetime] by default display 'UTC' string when displaying TZDatetime

[test] update test to avoid failure

[web] fix typo

[datafeed] fix stupid error introduced by 'just before qfinish' refactoring...

[schema] support for BigInt type. Closes #1720995

[test,i18n] update test and i18n catalog to follow addition of 'synchronizing' attribute on sources

[i18n] update yams error messages (requires yams#67668)

[datafeed] provide a source-sync command to launch source synchronization through the command line. Closes #1725692

[datafeed] use a boolean flag on CWSource to ensure we don't have concurrent synchronizations. Closes #1725690

[views] add columns parser and latest_retrieval to cwsource admin view

backport stable

Fix name error introduced in c21d845836e4 c21d845836e4 use a ``vocab`` variable but doesn't define it. I assumed ``vocab`` is ``field.vocabulary(form)``.

Fix conditionnal logic broken in 195b24fe3a03 195b24fe3a03 replace: if not req.cnx: by if getattr(req, 'cnx', True): The "not" diseapeared in the process.

[session] provide a simple transaction context manager for session. Closes #1725640

[formwidgets] make the select size a class attribute (more easily tuned)

[bfss] Make ``current_fs_path`` return None when an attribute has no value current_fs_path was returning the future fspath when no value was defined. * This does not make any sense * This tricks the storage into believing that updating the attribute content is not necessary. The file was written but the attributes was not updated. as a result the assignement was not made. (close #1725446)

[selectors] take care, Session has no cnx

don't crash if we can't fetch data or if xml is malformed

[datafeed] extract some methods from pull_data to ease writing custom datafeed sources

drop useless code