Update Schema queries from if else condition to getOrCreate formats

[debasishdebs]

Currently, for the following:

• Edge Label
• Vertex Label
• Property Key

We use a if else loop as gremlin query to first query for the element, if present retrive it or else create it as follows:

q = "if (mgmt.getEdgeLabel('{}')) {{" 
 "   {} = mgmt.getEdgeLabel('{}'); }}" 
"else {{" 
 "   {} = mgmt.makeEdgeLabel('{}').multiplicity({}).make(); }}\n".format(
self.label, self.label, self.label, self.label, self.label, self.multiplicity) 

This level of complex string formatting can be avoided by using JanusGraph's inbuilt APIs which does the same check.

Instead of we makeEdgeLabel in above example we will need to move to getOrCreateEdgeLabel and similarly for all other elements too.