Resolve "[bug] NodeForecastSolar: build_url doesn't build valid url."

Summary

build_url didn't cover the case of plane parameters passed as single values rather than list objects.

Explain your context

• covered above case to build url properly
• dropped support for help endpoint
• resolved timezone attribute (defaults to utc) not being added to request parameters (API would default to iso8601)

Closes #293 (closed)