998 show correct version list for children

This shall fix #998.

The child-ontology-versions were missing data (`commit_oid` and path-related data). This will now be created, for new data as well as for old data, the latter through a migration (which should be rollbackable).
Additionally i've added a `parent_id` field to ontology-versions. The field will refer to the corresponding version
of the parent ontology (read: distributed ontology) if applicable.

Additionally this contains an integration test which will check the corresponding view.

And just because some of this was annoying this pull-request comes with these features/fixes with **no additional charge** ;):

- Fix of cleaning redis after each rspec-example
- Remove deprecation warnings for mocha
- Remove mocha from rspec (explicitly use rspec-mocks instead)
- translate ontology_versions_test to rspec
- Remove migration-related error messages during tests
  - It seems the schema/structure was loaded during tests after `rake db:migrate:clean` was run.
    This resulted in the error messages, as it was a duplication of generating the database structure.
- Silence the output from using the git-repository factory
  - The factory uses system calls in order to create a sample git-repository, now the output is suppressed.

Also there was an error when introducing the new `iri-already processing` bit (merge-commit from staging).
Seems like there was a double-creation of permissions. Permissions (via hook) will only be created if they do not yet exist.
Style/FileName: Use snake_case for source file names.