Solr Dashboard main fixed

This is a Grafana dashboard that works OOTB with the Solr Prometheus Exporter. See https://solr.apache.org/guide/monitoring-solr-with-prometheus-and-grafana.html for setup instructions.

The dashboard shows a selection of metrics from

• Solr cluster-level overview
• Jetty (request etc)
• the Java VM (memory, GC etc)
• OS metrics (memory, cpu disk etc)
• Solr node (number of cores, threads etc)
• Solr Core metrics (index size, num docs etc)

Changelog:

• April 2021: New Solr Cluster row on top, showing number of live nodes, collections, shard status and shard leaders.
• January 2021: New Query metrics row, showing QPS metrics per collection (requires solr-exporter 8.8 or later)
• October 2020 version: Now the collection, shard, replica, core dropdowns on top actually filter the graphs!