caching and selecting of imported images from open clip art library

[rednammoc]

Going through the whole list of available open clip arts through the "import from open clip art library"-dialog is often a bit slow cause images are downloaded each time you select them. It would be nice, if already downloaded images would be stored in a cache. if there was also a dialog, where you can check those downloaded images, the whole process of selecting images from open clip art library would be real quick and quite an good user experience.