Various fixes

[mauritsvanrees]

I was testing https://github.com/plone/plone.classicui/pull/13 and this led to some improvements. See individual commit messages for details, but largely it is this:

• Do not export or import translations when plone.app.multilingual is not available. I got an error initially.
• Do not export or import discussions/comments when plone.app.discussion is not available.
• Add a fixer for the allow_discussion key: this should only contain True or False when this is explicitly set on the object.
• Blacklisted portlets were not imported when there was no accompanying change in the actual portlet list. Practically speaking: the distribution blacklists some portlets in the Members folder, but this was ignored on import.
• Export adds a newline at the end of all files. This matches the .editorconfig settings that we have in most Plone packages.

I have used this code to import and export a Classic UI site with the mentioned plone.classicui pull request, and have updated it.

BTW, is it too late in the portlets.json to rename blacklist_status to something like disallowlist_status? I don't feel strongly about this, but using "black" in this context is frowned upon. For backwards compatibility we could still read the old name as well.

[ericof]

I do not think it is too late to fix the naming in portlets

[mauritsvanrees]

In portlets I have deprecated blacklist_status in favor of disallowlist_status. We still read the old key for backwards compatibility.

And I added six news snippets. :-)