Add content settings (with region support)

[tidyui]

At the moment PrimaryImage and Excerpt is shown at the top of the content information, however this should be moved to a settings panel like it is displayed for Page and Posts. This way content will also allow displaying regions as "settings" as is possible for the other content types.

If neither PrimaryImage or Excerpt is activated and not settings regions are used the settings button shouldn't be shown.

If only PrimaryImage and/or Excerpt is activated and no other regions exists these could be shown in the main content area is they are the main content of the type.