Removed dead code
Button for manual reparsing of a specific ontology added.

closes #340
StateUpdater fixed and tested

should solve #430 and #405
Only retry ontologies without parent_id.
Only search for ontologies without parent on adding new commits.

related to #340
API for retrieving categories and category_ids
ontology header: show only defining files
add download link fo file view
Merge branch 'display-ontology-errors' into staging
Merge pull request #491 from ontohub/augmenting249_display_symbols_as_dag

Display symbols of OWL2 ontologies as DAG. Fixes #249.
Merge branch 'staging' into develop