Reduce calls to logging where possible in recursing as it's called so many times!
Don't call indent_tree for inoperable required unless in debug mode as this takes some time!
Flap Lever Synthetic can operate fix to be in keeping with derive method
 - Use Conf if available
Commented out debug logging of inoperable nodes as rarely used.
Fix conflict in FlapLeverSynthetic merge
Merge branch 'master' of github.com:FlightDataServices/FlightDataAnalyzer

Conflicts:
	analysis_engine/multistate_parameters.py
Docstring updates
FIX: slices_from_ktis  slice.stop is now exclusive
Stable Approach parameter improvements fixes (eventually committed!)
* Use average of two engine N1s for 8 secs
* Use of airspeed relative
* Use Combine Descent phase in place of Approach and Landing to include more of the descent
* Stable heading increased from 10 to 15 degrees to allow more roll when aligning to runway
* Vertical speed allows -1100 fpm (was -1000 fpm)
* A319 N1 limit reduced to 35% (was 45%)
* EPR limit reduced to 1.09 (was 1.10)
* No longer assessing engine stability only below 1000ft
Eng EPR and N1 for 10 seconds
Don't smooth Altitude STD signal twice
AirspeedMinusAirspeedSelectedFor3Sec added
Stable approach 
* updated to use N1 and EPR for 10 sec (was 5 sec)
* uses Airspeed Minus Airspeed Selected For 3 Sec in preferance to relative speed
Plot flight creates subgraphs when requested - much easier to use with
parameters of very different scales.
Addressed issues in test cases due to change from 'Takeoff Roll' to 
'Takeoff Roll Or Rejected Takeoff'
Stall Warning Duration KPV added
Overspeed Duration KPV only while Airborne
Fix FuelQtyAtLiftoff test case
FIX: node slices_to_kti where small gaps in signals
process flight cmdline api --tail supported in addition to -tail which is deprecated