Re #6897. New script to print out missing images.
Re #6897. Parsing image information in from the wiki docs.
Re #6723. Fixed up image file names.

 * Made them correct for case sensitive systems.
 * Turned spaces into underscores.
Re #6897. Adding image copying to cmake.
Re #6897. MediaWiki now modifies qhp more directly.
Re #6897. Added more options to checkmissing.
Re #6897. Adding a first pass at "ImageNotFound".

For images that don't exist in the filesystem use a default
crappy image that tells the user that.
Re #6897. By default ignore everything in the images directory.
Re #6897. Made missing image finding more complete.
Re #6897. Adding more image types to be automatically copied.
Re #6897. Adding logging and ability to download files.
Re #6897. Removing special characters from source code comment.
Re #6897. Adding help images to git.
Re #6897. More formatting of image metadata in qt-assistant.
Re #6897. Adding images explicitly to cmake.
Merge branch 'feature/6897_qtassistant_images' into develop