Revert "Merge remote-tracking branch 'globaleaks/devel' into feature/fields_refactor"

Branch "devel" is broken on my system, with a "KeyError on 'node'".
I am reverting the merge as @evilaliv3 did not took care of fixing the bug, and
I have to proceed with the development of fields.
This reverts commit 731bb15e466c13ab207677084a85071f507cd1cb, reversing
changes made to 71b10d5c264adac635ab30e5c271240fa01e6864.
Implementing post request for /admin/field/step/.

Add rest api for handling step creation.
note: still have to register the handler.
Implement draft for PUT requests for /admin/field/step.

Add rest api for handling step update (i.e. rearrange).
note: still have to write proper unittests.