Bug/Changes: Plugins cannot be loaded into Grafana

Several changes needed:

• unzip -j will unzip everything into a flat structure, removing sub-folders. This will not work here because Grafana validates the integrity of the plugins on loading (and expects the folder structure to be exact)
• Pie chart plugin is part of the core plugins for Grafana now and doesn't need to be added on.
• Download link for the redis plugin is not Github which is okay, but keeping them consistent seems better.