Add network visualizations

[maciejjan]

It would be nice to have an easy way to share visualizations in form of a network.

Examples:

• neighboring clusters (move from Runoregi)
• similar poems (move from Runoregi)
• word co-occurrences
• custom SQL (edge list)
• custom CSV (edge list)

The problem is that data for network visualizations like similar poems/clusters requires several SQL queries (one per each depth level) to fetch, so this would require some redesign of the configuration format. Is it worth doing?

The visualization could use the visNetwork library (see here).

[maciejjan]

Whisker's looping functionality could be used to add SQL subqueries for each depth level. Would this have acceptable performance?