no self._cw on widget objects while '_' is defined locally

delete remaining stuff w/ handling of the generic relations

test update

clear vreg's parent_classes cache to fix etype cache / auto-reloading bug EtypeRegistry.parent_classes()'s is cached. When the registry is reloaded, if the cache is not cleared, we might get the old list of parent classes and that leads to strange bugs. Typical scenario : 1/ start application in debug mode 2/ go to add/Bookmark -> everything's fine 3/ change the source 4/ reload add/Bookmark -> 'creation' not selectable because : a/ cw detects a change in the source and reloads vreg b/ cw tries to select 'creation' view for 'Bookmark' - 'creation' view uses specified_etype_implements('Any') - cw compares Bookmark.__bases__[0] (i.e. new version of AnyEntity) with the old version of AnyEntity cached in the vreg. They don't match => view is not applicable.

merge

fix bad indent

backport stable

cleanup

fix bug: the 'table' argument is overwritten by the loop variable, causing latter crash due to this missing information

don't record deambiguifier when it has no type restriction using 'is', so we don't miss later some available constraints