Add Coupled Operations to SFG

Description of issue:

Coupled operations should be able to be added to an SFG by just adding one of the operations to the SFG. The SFG should preserve the coupling between these operations.

Linked Requirements:

( 20 )

Potential Issues:

None

Blockers:

( #8 (closed), #12 (closed) )

Issue Requirements:

1. A chain of coupled operations should be able to be added to a SFG.
2. Coupled operations added to a SFG should preserve their coupling when added.

Comment:

None