TYPO3 Core

In some cases where the BE users only get one content element due to access restrictions (for example text), all the other empty categories (plugins, ...) are shown anyways. This should be removed to make TYPO3 easier to use, and if there is only one type of content element left, it could be automatically selected.
The same applies to the position of the content element on the page. If there is only one possible position (like it is on an empty page with just one column allowed), the wizard could auto-select these options.

Hopefully, this change will make TYPO3 easier to use in environments where the users have no technical experience.

(issue imported from #M1571)