[entity doc] fix typo (rest_var instead of rest_attr) and cleanup doc

[exceptions] stop catching any exception in various places (closes #1942716)

[tableview] fix view selection when value is None (closes #1936781) * in case of None on final view, use explicitly asked view anyway * when etype is None, that means it's a non final entity type

[book] merge pyro chapter with faq entry with connexion snippet

i18n update

[schema view] fix label/name inversion leading to wrong css class / group url depending on user's language

[i18n] tweaks

[i18n] cleanup messages moved to localperms cube

[security view] slight changes to make things clearer

backport stable

[refactoring] introduce add_etype_button function to properly create button to add a new entity also properly use cw_create_url to generate the URL to add the entity

[user prefs] use same title as the action for consistency

[sources management] properly set __linkto, closes #1922970 when clicking on 'add mapping part' on an external source view, one expect to have source properly selected in form

some minor cleanups

[web test] fix test broken by new users/groups management views

[table view] allow to set None in 'headers', meaning the label should be fetched from the result set as done by default (closes #1931533) the point of this is to avoid having to define the whole headers list when only some of them have to be defined.

[user management] users and groups management now really lead to that (closes #1931478) ie, one tab for users, another for groups. By default the groups tab simply list existing groups (with the number of users they count), and propose to create a new group.

[css] use h* title properties from uiprops in cubicweb.old.css (closes #1931476) + minor cleanup of cubicweb.css

[entity fetchattrs] also fetch ambiguous rtypes even if we do not recurse on them (closes #1720823)

backport stable

[jquery] upgrade to jquery 1.6.4

[test] fix some tests broken since localperms cube extraction

refactor entity fetch_rql method to use a RQL syntax tree instead of RQL strings ; closes #1585650

[doc] add some documentation in cubicweb.web.action