Refactor file storage

[miyurud]

Currently, the partitioned graph data of JasmineGraph gets stored in org.jasminegraph.server.instance.datafolder and we have set its value by default to /var/tmp/jasminegraph-localstore. Instead of that we need to change the folder name to /var/tmp/jasminegraph-datastore. Furthermore, need to change this single folder to hold all the data of JasmineGraph.