after an owl ontology is imported the entity tree is generated
fixing error with pagination and entity tree
tests are green again
cosmetic commits
Merge branch 'staging' into 249-display_symbols_as_dag

Conflicts:
	app/models/ontology/entities.rb
Refactoring and fixing of two issues:

* First click on entities#index showed hierarchy _and_ details views.
* Hierarchy was not correctly built (maybe because of wrong error raising on
  detected circle).
Merge pull request #552 from ontohub/249-display_symbols_as_dag

Generate entity hierarchy for new OWL ontologies and fix bugs with hierarchy view. Related to #249.