fix broken links

[VladimirAlexiev]

hi @SvenLieber !
There are many broken links:

• https://unshacled.com/ is down
• the images in here are broken:
  https://w3id.org/imec/unshacled/spec/shape-uml/20210118
  https://w3id.org/imec/unshacled/spec/shape-vowl/20210118/
• the images are ok in the latest spec versions
  https://lov.ilabt.imec.be/unshacled/spec/shape-uml/
  https://lov.ilabt.imec.be/unshacled/spec/shape-vowl/
• these README sections are missing:
  https://github.com/KNowledgeOnWebScale/unshacled#Model
  https://github.com/KNowledgeOnWebScale/unshacled#Translation
  https://github.com/KNowledgeOnWebScale/unshacled#Interface

Finally, could you include some images in the README of actual shots with unSHACLed?
Does it look exactly as in the spec, or are there differences?

ShapeUML:

ShapeVOWL:

[BigBlueHat]

I added one screenshot to #3. Maybe I should add another...

I added UML and VOWL screenshots in #3 fwiw.