The spark charm currently grabs Spark-Bench and sample data for the pagerank benchmark from s3. This is not good for a couple reasons:
1 - Spark-Bench hasn't been verified with Spark 2.1.0.
2 - Deployments might fail in an environment where the charm is not allowed to fetch things from s3.
#1 is an easy fix; just change the default behavior. SB is there if a user wants it, but we shouldn't install it by default.
#2 is trickier because we do need the sample data for our pagerank benchmark. Refactor this as a Juju Resource (vs s3 URL) so it comes from the charm store.
While we're here, simplify the spark charm library to remove leftover cruft from pre-Bigtop days and break out the complex configure method into more purpose-optimized methods.