Move AwaitGraphIndex and UpdateIndex out of Index builders

[debasishdebs]

Now, when a Index query is build to create an Index, the set of queries being submitted to Server contains queries for

• Creating Index.

• Await till Graph Index is in Installed state.

• Update Index into existing data.

We need to move the last 2 points, i.e. awaitGraphIndex and updateIndex out of Index builder so that user can invoke it based on their needs. Like UpdateIndex isn't required if the schema loading is first thing being done on graph.

The syntax to be followed would be:

graph = JanusGraph().connect()
mgmt = graph.openManagement()

index_builder = mgmt.buildCompositeIndex("indexName", "Vertex")
index_builder.addKey("prop1").addKey("prop2").indexOnly("label1").unique().make()

mgmt.awaitGraphIndex("indexName").make()

mgmt.updateIndex("indexName").make()