index_at_value_or_level_off  library routine extracted from flight_phase Go Around and Climbout to support its use in Approach And Landing which will benefit from this routine.
ApproachAndLanding updated to use climbout or level off as per goaroundandclimbout as an improved method of extending the go around phase - without this it is easy to created slices where the start is None.
Blend parameters accept None types in list of sources
blend_parameters now accepts None available sources
blend_parameters now accepts None available sources
Wheel Speed merging - using updated naming convention of (L) (*) and (R) (*) sources.
Merge branch 'master' of github.com:FlightDataServices/FlightDataAnalyzer