closes #1784285: [rql2sql] crash when using a relation for inner and outer join

[range facet] closes #1806937: simply retrieve min/max values when computing vocabulary/possible_values, this is enough

[facet] fix facet values update, broken by 7626:56300bec75f8

[facet slider] quote attribute value, else may break with earlier jquery

[facets] use unique dom id

[facet] with rql path facet rel may be None, handle it

[facet] closes #1806932: test and fix facet bug w/ having query (need rql update)

[ajax js loading] when everything is already loaded, don't do anything

backport stable

[IE, plot] ship with jqplot'excanvas version (include http://code.google.com/p/explorercanvas/issues/detail?id=82 for instance)

[etwist, modconcat] closes #1806935: directly write data, don't put the whole concatenated thing in memory

[etwist] clear ui cache at server startup time. Closes #1806933 this avoid pb when cubicweb/cubes provide new version of some js/css and also accumulating junk in the cache directories

[facet] closes #1806931: new facet type, based on arbitrary rql path

[selectors, test] remove duplicated test and add some for relation_possible selector w/ rqlst

[repository] catch Exception instead of everything

[facet] fix argument inversion in date range facet

[facetbox] put the facet box in a box

[doc] fix broken links

backport stable

[test] fix test, code from 3.13 gone in 3.12 accidentaly

[selectors, facet] make is_instance and other EClassSelector subclass gather entity classes from 'select' and 'filtered_variable' context information. Closes #1796732 This allow for instance to use the filter form on rqlst where the filtered variable is not selected

[facets] DontUpdateConstraint mecanism introduced a few commit ago isn't needed: we already have the 'needs_update' property controlling this

[facet] more api cleanup: support_and should be a property, so it's easier to deactivate.

[range facet] refactor to ease overriding, possible_values raise DontUpdateFacet (not handled by js actually)

[facets] allow to specify on which rqlst's variable facets should be applied. Closes #1795915

[facets] refactor / cleanup facet api: more consistent variable naming and easier to reuse function. Closes #1796804

backport stable

[schema / rql] fix mainvars of RRQLExpression with parens

[facets js] better cubicweb:facetargs handling and avoid initializing a same form twice (that may occurs)

[facets] should remove groupby from base rqlst. Closes #1796196 as we search for values for a variable, there seems to be no case where we would be interested in groups, though there are clearly some were leaving groups cause errors.