prepared Metadata Tab for #228
Merge branch 'augmenting214_new_design_of_ontology_metadata_tab' into augmenting228_domain_field_properties
add icon images for ontology classes.
Debugger added
Gems updated
move vector graphics into assets directory.
Merge remote-tracking branch 'origin/staging' into augmenting213_ontology_class_icons
include ontology-class icons into fancy links.
link content-tab to children for DOs

- The content-tabs usually links to entities,
  but DOs do not have entities, so we link to
  the children instead.
center the icon for single ontologies.
use ontology-class icons for ontology title line.
add tasks to ontologies
updated ontology model, ontology_type seeds
Merge pull request #255 from ontohub/correcting162_create_versions_on_children

Correcting162 create versions on children
add license model to ontologies
renamed seed module
test tasks for empty name
add formality_level to ontologies
migration not committed
merge nav_helper