Revise Complex type documentation

The changes made for https://github.com/Azure/autorest.powershell/issues/321 are not that great and could be cleaned up quite a bit. Based on Cormac's suggestion, we would, instead, display the type information instead of having it organized by parameters. Changes include:

- Display list of complex types (not parameters) in Notes section
- Nested complex types would simply show a link (markdown) to the type definition
- Flattens display of all types, since it would only show 1 level deep for each.
- Parameter descriptions would contain a link (markdown) to the type in the Notes section