#2238: Add a media library to the Image Editor

Add a media library to the SVG-Editor like the existent on the article editor. That may be a SVG-Editor plugin.

Must allows to:

• find images (any supported type)
• Include images
  • If that is a SVG, include elements
  • If that is a Bitmap, referrer in a <image> tag
• Upload new needed images

This feature depends on ActionItem2237