1 SKOS API Support #625

[giraygi]

This pull request includes the following features for #625 :

• SKOS Full Concept Tree Generation
• SKOS Partial Concept Tree Generation down from a certain concept
• Enabling to retrieve immediate neighbors of a particular concept based on relation type (related, broader, narrower)
• Plain Text Versions of the above three needs in order to provide human readability for alternating graph generation techniques based on (SCHEMA, TOPCONCEPTOF, RELATIONS)
• An immediate neighbors graph that the subject node targets based on relation type (related, broader, narrower). This graph is intended for visualization.