Report maxStoreFileCount in jmx

We currently report metrics like storeFileCount, maxStoreFileAge, etc. These are provided at the regionserver level and table table. We should also report maxStoreFileCount, which would be aggregated across all regions on the server or table(s).

This metric would be helpful in ensuring we don't get too close to the {{hbase.hstore.blockingStoreFiles }}limit before running compactions or slowing writes.