Add option to connect to Gen3 systems

[kellrott]

Build configurable mode where Funnel utilizes a Gen3 ( https://gen3.org/ ) as management system for authentication/authorization and DRS id resolution

• Recognize HTTP headers used by Gen3 clients
• Connect to Fence ( https://github.com/uc-cdis/fence )
• Connect to Arborist ( https://github.com/uc-cdis/arborist )
• Build way to utilize Fence URL signing to access file system
• Submit generated files back into Gen3 after completion of job