Added class 'Thing' to Subject-Dropdown

The anonymous class 'Thing' is added to the loaded subjects from the
endpoint. It will now also be shown in the subjects dropdown near the
workspace.
Changed URI of special class Thing

Renamed uri of Thing-Class to dbpedia-ontology-uri.
For Things: Rerenamed URI & added all properties

The URI of special class thing must not be ontologies uri. This is
changed now. Additional the query for getting a subjects properties is
now also adjusted for the special class Thing.
Made a special Property add-able

The alias is '???'. Feel free to change it if you have better ideas. The
property is available in every class. At the moment it is only
"combinated" with special class 'Thing' as object. I'm working on
improvements.
Fixed translation

Changed translation:
- For 'Thing' no line like     ?thing a <uri>.
- Deleted double '?' in property-translation. (second one is in y)
Fixed translation of properties

It is necesssary to tailor the URI of properties because they have URIs
like:

<http://dbpedia.org/ontology/Person/weight>

but <http://dbpedia.org/ontology/weight> is needed.
Translation of specialProperty

Fixed the translation for specialProperty.
(URI-fixes in triples and shown-values changes)
Added specialProperty for DatatypeProperties

First specialProperty was only a ObjectProperty, now both types of
properties are available.

The are now also renamed.
(before: '???' now: 'unknownConnection' and 'anknownProperty')
Commented the specialConnectionProperty

In allClassURIS should be the URIs of all classes. At the moment it's
only one ('Thing's URI). I'm working on it.
Wrote functions for specialProperty

UnknownConnection-Property allows every Class as a link-partner now.
New problem: The special classes are no longer shown in the property
container. Watch factory.getProperties (espacially line 208) if you want
to fix it.
Added optionality for properties

Button to toggle between optionality of a property instance
Added optionality for inverse properties
Prepared JSON-save-function

Button and event added.
The function 'saveAsJSON' in 'translatorManager' will be filled with
saving-functionalities. At the moment there's only an alert showing the
JSON-content.
Merge branch 'optionalProps' into develop

* optionalProps:
  Added optionality for inverse properties
  Added optionality for properties
Added correct operators for all property options (inverse and non inverse).
Fixed translator syntax regarding inverse properties.
Fixed handling of 'optional' properties in translation to SPARQL.
Added String-Property.
Fixed String Comparison.
Minor bugfixes regarding too much ???
Added Language Selection to StringProperties.