3178: Add missing jobs.create and users.setup parameters to discovery document.
3178: Use different discovery doc cache files for different API servers.

Also port "use api even if discovery cache file can't be written"
rescue block from arvados-cli to arvados gem.
3178: Discover required parameters for regular CRUD methods, too.
3178: Merge bogus _setup_requires_parameters into existing class method.
Merge branch '3178-discoverable-parameters' closes #3178