LDaCA schema visualiser

[spikelynch]

• [x] Show precis of all the entity types
• [x] Show precis of all the relation types (properties)
• [x] Show precis of all ids, including ones not in the graph
• [x] Summarise external ids by domain
• [x] Make controls for all of the above so user can select which ones to visualise
• [x] Use these controls to drive a force graph
• [ ] Use these controls to drive a tree