Fixed name error in ThrottleReductionToTouchdownDuration.
Added frequency to create_kpvs_from_slice_durations in HoldingDuration
Resolved conflict in key_point_values.
Removed conflict in key_point_values.py
Merge branch 'master' of https://github.com/FlightDataServices/FlightDataAnalyzer
Fixes for ElevatorActuatorMismatch derived parameter node.
== None changed to is None.
Removed commented line.
Code tidying and documentation changes.
Merge branch 'master' of https://github.com/FlightDataServices/FlightDataAnalyzer
Refactored TCAS events and changed to using correct TA and RA states

Added TCAS TA Warning Duration event.