Implement a Benchmarking section (front end interface for basho_bench)

[dmitrizagidulin]

Once the API-side basho_bench integration is implemented, provide the front end UI for it:

1. Add a Benchmarking section to the Cluster Ops view.
2. Provide the ability for users to select from a small list of basho_bench config templates, and edit them in a textbox (read-only test, write-only test, 50:50 read/write). Query and CRDT templates can be added later on.
3. (Optional) As an alternative to editing a config file in a text box as above, implement a Benchmark Builder interface (select operations mix, duration, concurrency, key and value functions, etc).
4. Provide the UI to launch benchmarking runs, and to display result summaries / graphs.