add version numbers to version index view
add download links to ontology version index
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
define method for external ontology creation

This method should be a part of ExternalRepository, as this class
handles everything representing the external repository. So it seems
right for it to contain a ontology-creation method.
create basis for Ontology-ImportModule replacement

the Evaluator class should be the core of import
module replacement. However it shall get a
specific NodeEvaluator class/object which will
take the heavy lifting (which will do
the actual ontology handling).
create basis for the hets node evaluator.
redefine the listener of ontology-parser as class

Although the listener was already a class, the new
callback mechanism, which is not based on procs any
more, needs some adjustments. And as this is closely
coupled with hets, it should be the hets module
which contains this class.
add new baseclass for actual parsing (XML).
create a helper for node evaluation.
Add the actual NodeEvaluator class

This class is what actually replaces the ontology-creation
content of import.rb.
let import-methods use Hets::Evaluator.
let specs use Hets::Evaluator.