mattdrayer/api-signal-flag-common-aws: Added feature flag to settings fi...

...les

@chrisndodge @fredsmith -- added the signal and gradebook flags to common and aws settings files -- let me know if anything more is needed.
Oops. THis isn't correct, you shouldn't reset the FEATURE flag here as it was read from a .json file from disk up above. Just remove this line (467)