Allow initiation of OpenIDSession from outside of stapler by refactoring methods to support both Stapler and plain-old-servlet invocations. Maintains backward compability with existing usage.
Revert "Allow initiation of OpenIDSession from outside of stapler by refactoring methods to support both Stapler and plain-old-servlet invocations. Maintains backward compability with existing usage."

This broke the CLI

This reverts commit 57b74a1c04ee9e5f7f4c778085c13a47bddfff89.
Optionally accept a "from" parameter in commence login. This allows logins with pure 302 redirects instead of existing javascript redirects. Will now default to the root URL if neither parameter provided.