Hercules extensions to Derived Parameters
Magnetic Variation at 1/4Hz for non-superframe ac
IAN naming added

names added for IAN Glidepath Deviation and IAN Final Approach Course
Deviation. These are named dynamically, but the absence of a name led to
both upper case 'IAN..' and mixed case 'Ian..' versions appearing in the
list of nodes to run.
Airspeed Minus V2 operating from AFR

When an AFR V2 is provided, there is no lookup table, so the node needs
to operate without V2 Lookup in the available list. V2 is picked up from
AFR V2 in the derived parameter node for V2.
removal of temporary vertical speed params
raise error to make issue more clear when can't find touchdown point below 20ft
ThrustReversersDeployed now allows deployment for the entire landing phase - unlikely but possible if phase is cut short.
library comments
Merge branch 'master' of github.com:FlightDataServices/FlightDataAnalyzer
AltitudeSTDWhenDescending NAME now name
blend_two_parameters trap for both None
Touchdown correction

Special case of touch peak value at start of array leads to scanning for
an argmax over an empty space. Restructured to avoid this case.
Hercules flap settings extended for t/off & ldg
Touchdown graphs inhibited
changed flare duration 20ft to touchdown to use 20ft above the height at touchdown.
Merge branch 'master' of https://github.com/FlightDataServices/FlightDataAnalyzer
V2Lookup and AirspeedReferenceLookup parameter requirement of "Eng (*) NP Avg" added to derive method to enable can_operate functionality.
Merge branch 'master' of github.com:FlightDataServices/FlightDataAnalyzer
changed takeoff roll to use first order washout to reduce impact of variations in slope of runway
Merge branch 'master' of https://github.com/FlightDataServices/FlightDataAnalyzer