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.
convert ontology_import_xml test to rspec

Also use new Hets::Evaluator.
convert sentence test to rspec

Also support Hets::Evaluator.
convert ontologyversions controller test to rspec

And use Hets::Evaluator in the process.
deactivate parser tests.
enhance documentation base evaluators.
move some methods into evaluation helper

As these methods are used during the course
of parsing the DGXML - this means that they are
directly called by callback-methods - they
should be placed in the helper module.
fix alignment issues.
fix language in comment and spec-description.
use let! instead of manually initializing version.
Merge branch 'staging' into 649-refactor_parsing

Conflicts:
	app/models/ontology/import.rb
Merge pull request #943 from ontohub/649-refactor_parsing

649 refactor parsing