Changes

[G4] Persistent object support
 (commit: 49cf92f)

Improve smoothness of ff_interpolation
Changes:
- identify different types of duplicate packets
- handle each error differently
- individualised responses to duplicate packets, and to the packet after
that
- boost on yaw
- FF smoothly attenuated while sticks are near centre
- no boost immediately after prolonged flat spots
 (warning: this means no boost if ADC is on)
- careful empirical checking that the responses are optimal
- updated code annotations for clarity
 (commit: cc3d0b4)

add marker for center suppression
 (commit: f93cda0)

Revert to single blip up and down
 (commit: 2f1afdf)