Get the singleton SQLContext if it exists or create a new one using the given SparkContext.
Get the singleton SQLContext if it exists or create a new one using the given SparkContext. This function can be used to create a singleton SQLContext object that can be shared across the JVM. This is a bit of a hack over the regular Spark version, we re-create if the Spark Context differs.
Utility companion object to provide getOrCreate on SQLContext