Make YAML template easier to read

- Use folded block for Description
- Clarify description text
- Don't use JSON-style notation for Parameters
- Join UserData script with newlines to make it more readable
- Rename nonsensical 'WikiDatabase' instance to WebServer

Change-Id: Ieb7925e3fdb0e7f65fd6f69b9e9bbcd0235587da
Merge "Make YAML template easier to read"