Add option to display images inline for annotation values

[matthewhorridge]

For annotation values that are URLs that point to images it should be possible to display thumbnails of the images inline.

[csnyulas]

This works only for image URLs that are specified as IRI annotation values, but not for URLs specified as literal annotation values (such as xsd:string, xsd:anyURI, or even literals of unspecified types).

[csnyulas]

BTW, it should work for GIF images as well, which is currently not supported.

[csnyulas]

Images reference by a local file URI, such as file:///home/user1/Pictures/pic1.png, are not shown.
It would be definitely nice to show those, as well, in addition to the http URLs.

[csnyulas]

And, BTW, annotation values that contain other text besides the image URLs do not get the URL replaced by the image. For example:

blablabla https://assets-cdn.github.com/images/modules/logos_page/Octocat.png blabla continued
or even if the image is in a separate line like this
https://assets-cdn.github.com/images/modules/logos_page/Octocat.png
it is not displayed.

Not sure, if this is a problem that we want to fix, of not, but I thought I make a note.