Refactor files and sidebar to accomodate the new Programs section.

[johnnymatthews]

The sidebar and underlying docs content need moving around to reflect the upcoming Programs section (see #269).

Tasks:

• Review and analyze existing structure.
• Update Markdown to fit new structure.
• Review and update cross-linking and references.

Mechanics:
- What they're made of (WASM)
- Who's gonna interact with them (validators)
- What they can do (generate a signature to the validators, or fail)
- What they can't do (interact with non-deterministic data, return a result other than a signature or failure)
- Program lifecycle (how are they made, read, updated, and deleted).

Development
- Create
- Deploy
- Update
- Delete

Testing

Troubleshooting

[johnnymatthews]

Merged into #269.