feat(revisions): move code from separate page to widget

SD-503
feat(revisions): improve revisions widget

Add preview functionality

SD-503
fix(api): use resource links for subresources

instead of adding subresource to self.href it will use subresource
uri template from `/` endpoint
fix(lock): don't display my opened items as locked

locks should be only visible to other users
feat(lock): view only mode if an item is locked
fix(authoring): remove it from sidebar menu