[test] must now commit file creation since the later ValidationError trigger a rollback

cleanup and micro-optimization

[web action] has_editable_relations should not filter out final relations, fix regression introduced in 6358:22c95c5ef12d

[c-c] fix RuntimeError: 'maximum recursion depth exceeded while calling a Python object' we get when creating/upgrading/shelling an instance: hasattr() call __getattribute__, creating an infinite recursion error catched by the interpretor. Avoid this by testing the method is available on the class instead of the instance

[transaction] to avoid potential db corruption, we should rollback systematically in case of ValidationError

[selector] cleanup

[sync schema] take care rdef may not be final, in which case we want to use type of eid attribute

[web action] has_permission_update checked implicitly by has_editable_relation, don't check it twice

[muledit] form may contains subforms with nothing editable that will be s kipped, so ensure we choose one with something to display when rendering table headers

[c-c i18n] namespace/line wrap cleanup + dynamically compute available language + make it works in installed mode