[pkg] prepare 3.17.4

[pkg] merge centos 3.17.1-2 in stable (prepare 3.17.4)

Added tag cubicweb-centos-version-3.17.1-2 for changeset 965f894b63cb

[rqlrewrite] fix rqlrewrite unpredictability vs relation sharing. Closes #3036144 The relations index used to determine if relation may be shared only considered a single relation node per relation type. So when the same relation type occurs several time, dict order give unpredictable result. We shall properly consider all relations instead. Tentative test case included (but bug reproduction is by definition unpredictable...)

[rqlrewrite] rewrite doesn't need a solutions argument, always use the Select'ones Also, do a copy systematically else it may lead to empty solutions depending on the rewrite path. Test case tentative included in the following changeset.

[rql rewrite] equivalent but much simpler flow

[pkg] Prepare a new RPM release

[pkg] Add log directory to rpm

[repo] normalize ValidationError on edited entity (closes #2509729) In CubicWeb, ValidationError.entity MUST be the eid of the involved entity, not the entity iteself (as done by yams).

[doc] one must now manipulate the req.session.data dict (closes #2842345) instead of deprecated get/set/del_session_data methods.