Create a "entity" page

[matentzn]

Create an entity page like

http://localhost:8081/spot/oxo2/entity/MA:0000358

This page should contain

• a table which shows all the mappings from this entity
• a table which shows all the mappings to this entity
• a facet to select how many hops should be checked (1, 2, 3, default 1)
• a facet to select predicates allowed for the chaining
• When facet 2 or 3 is selected, the API needs to be queried. For this we need to extend the API in a way that it allow this. I would suggest to extend the "chaining" endpoint, that
  - Takes as an input and entity, a set of predicates and a number (hop count)
  - returns a set of intermediate object_ids.
  - These can then be used to query the normal "mappings" endpoint to get all the relevant mappings.

The last needs some careful thinking by @anitacaron, I am not so sure if I got this right. No pressure now though.