adjust parse-specs for ontology_version_id check.
handle local files for external repository

Probably only needed in tests, but may prove
useful for other usecases too.
set ontology_version_id always.
create update_version! method and use it

This includes setting the version, if a new version
is created through the update_version controller action.

Also compact is used on versions before iterating to
filter out nil-values (result of versions.current being nil on some
test-ontologies).
define current_version method and use it

current_version will use ontology_version, but will
fallback to versions.current if necessary.
add specs for permissions check for git/ssh.
pass specs and add private_* support to git/ssh.
extract permissions-check (git/ssh) into methods

Thise includes the following:
  - Everyone-Case
  - Permission-based handling
  - Role-based handling.
Merge pull request #894 from ontohub/232-use_ontology_version_id

232 use ontology version
use boolean in git/ssh instead of if-elsif-else.
add version numbers to version index view
display newest version first
use bootstrap modal in file edit on discard
Merge pull request #900 from ontohub/898-handle_private_repositories_for_ssh

898 handle private repositories for ssh
Merge pull request #913 from ontohub/500-newest_version_first

display newest version first
add download links to ontology version index
move modal functionality into discard()
use ontology.repository; repository does not exist

repository does not exist anymore (is not set in the controller),
so we'll access the repository through the ontology.
Merge pull request #919 from ontohub/hotfix_oops_repository_path

use ontology.repository; repository does not exist
Merge pull request #912 from ontohub/886-incremental_version_numbers

add version numbers to version index view