Remove versions_history_form

[mauritsvanrees]

In PR #81 I have moved this skin template to a browser view. But I think it is best removed, because it is mostly a duplicate.
Our versions_history_form is roughly the same as @@historyview in plone.app.layout, which is a small wrapper around @@contenthistory in plone.app.layout, which is a viewlet turned into a view. Their version looks nicer. But our versions_history_form has a preview (which contenthistory points to) and a form to add a new version, if the policy is manual.

So:

• Move the preview to contenthistory in plone.app.layout. Or make it a separate page that still lives in CMFEditions. Possibly let contenthistory load it as a popup.
• Move the form to add a new version into contenthistory.

BTW, I saw a couple of CSRF errors when working on the PR yesterday. Not sure which template or view causes this. Would be good to check.

[ale-rt]

I noted that as well, the error do not show up when working with the @@historyview.

[pgrunewald]

I stumbled upon the CSRF error as well. It is caused how the link to the versions_history_form template is being constructed. The link from @@historyview has the plone.protect-token ("authenticator") included.

Compare:
from @@historyview: http://localhost:8060/Plone/hello-plone/versions_history_form?version_id=3&_authenticator=924bf3698b0ec56922c3639e161f33516b6602c4#version_preview
vs:
from versions_history_form: http://localhost:8060/Plone/hello-plone/versions_history_form?version_id=3#version_preview

This token basically allows the write operation of an temporary attribute (done in retrieve() in CopyModifyMergeRepositoryTool.py). Anyhow, this issue is revolved, when we stick to the solution in @@historyview.