remove duplicate class members

Summary:
Flow currently allows duplicate members on classes. At runtime the "last" member wins out and all previous values for the member are discarded.
This diff manually removes duplicate members, and fixes resulting flow errors by converting methods to arrow function properties.

Reviewed By: pieterv

Differential Revision: D33664966

fbshipit-source-id: 0f712ac96af4df593c0918fcbadd70624ddde4a6