Updates - 787/flap/AP/

Derived parameters - autopilot engaged status better caters for triplex
AP
Flap handle can be derived from flap surface or flap lever, in either
case triggering a change of state at the first movement of the control.
Flap (i.e. the actual control surface) now changes only at the end of
the flap movement, not at the midpoint.

Library is_5_10_20 a small function to allow for Boeing 787 signal
sample rates
align method now accepts 787 sample rates.
Clip function minor corrections
peak_curvature refined to allow for a greatest curvature not in the
sense being monitored; it will be ignored and the signal scaled to
detect curvature in the required sense only. (In fact this error was
found when working on flap settings, but not included in the final
solution).
step_local_cusp function added to detect change of slope, especially in
small data sets, to suit step_values function.
step_values extended to monitor at start or end of control movement.

library_test additional tests added to suit the above.