include current path in login link
reformatting code
path *can* contain / !
improved admin/contents navigation for childless content
provide working cancel button links

Fixes issue #521
.o is deprecated; use .instance
cleanup
Split form using an accordion; make sure on error all relevant accordions are opened
some different controls / ux experiments
hide testing field
generic base template for admin, not only edit
fix testcase where parent is None
refactor split form into base, reuse for create/update
redundant whitespace