Create task driven flows documentation

From documentation planning session on 20/10/21.

Need explanation of how to set up flows.

Gather flows content into one section ... set up, telemetry, using Helm to view, etc.

Section may eventually include Nephron documentation.

Splitting this into separate tasks for the following phases:

Phase 1: "Basic" - OpenNMS core in the data center receiving flows, the minimal possible setup
Phase 2: Minion in a remote network
Phase 3: Sentinel to scale write performance
Phase 4: Nephron for aggregation

Docs will have the following structure:

Flows

• Intro
• Basic flows
• Application Classification
• Remote flows (with Minion)
• Scaling flows (with Sentinel)
• Streaming telemetry with flows (with Nephron)
  • ** NOTE: Nephron docs will be in the Nephron repo. Will need to create cross-reference in main docs once Nephron repo has the docs.
• Troubleshooting flows
  • Basic
  • Remote (with Minion)
  • Scaling (with Sentinel)
  • Streaming telemetry (with Nephron)