Moved PLATFORM to its own module.
arranged modules so core comes first
Split OpenFlow0x01 in to _Core and rest.

This is an intermediate point in the refactoring.
Revert "Split OpenFlow0x01 in to _Core and rest."

This reverts commit 040d3bb5785215ea77ad025b887c0019171cea6d.
Moved Match.t -> _Core.pattern
Moved PseudoPort to _Core
Moved Action to _Core
Moved flowMod to _Core
Moved payload to _Core
Moved packetIn to _Core
Moved packetOut to _Core