Common prefixes instead of random prefixes

[Anoop-Variyan]

In the prefixes shown in the turtle view in the open data explorer, it would be great if the prefixes are the common prefixes instead of random prefixes. For example, in the highlighted one in the image, it should be epo instead of ns2.

[rousso]

Duplicate of #28.

[rousso]

This is addressed in PR #67 (via #28).