[server] improve the speed of setting relations between entities (closes #1625257) The main idea is to add methods equivalent to session.add_relation and repository.glob_add_relation which handle several relations in one call. Speed gain results from: * using cursor.executemany to run SQL statements * factorizing some code which otherwise has to be performed for each relation, such as context manager creation before calling hooks or to enable security, creation of the EditedEntity instance (when several inlined relations are set on a single entity, and consequently when refreshing the cached entity) benchmark runs 1.1x faster for non inlined entities and 125x faster for inlined entities :-)

added test case to monitor speed improvements in the repository code. To use it, add a test in a patch, then hack CW to speed it up in another patch, updating the test if needed. By running the test with and without the second patch applied you can easily see the speed improvements

backport stable changes to default

[js] update jquery.corner.js to the latest version (uses native css support for browser that provide it); closes #1625065

[js/css] remove old versions of ui.tabs/slider etc.; closes #1625085

[devtools] make return value of get_response_header(raw=True) consistent wrt get_header(raw=True) i.e. get_response_header(raw=True) now returns the first element of the list rather than the list itself.

[widgets] handle no value label for tristate radios, put default separator on class for easier redefinition - closes #1624839

[doc] update of the update

[tz postgres support] we've to commit the connection once time-zone is set, else we may loose the setting

[tz support] more tests