Improve Graph view of the registry

[rzadp]

• Add label/title to a link (the title would be a tag like beta, or a version like 1.0.0)
• Enable multiple links between two nodes

For example, I can have 1 record node, 1 resource node, but 2 links between these two (a tag link and a version link). Right now it does not seem to work.

For example I have 4 different links:

But the graph shows only 2: