Integrate updated & blend_two_params amended

Integrate options extended to allow function call to extend across
masked data to end of array.
Blend Two Params now asserts that the offsets are different to prevent
blending two copies of the same parameter pointlessly (as has happened
due to misread LFL documentation).
VSI corrected for 0-100ft inertial segment.
Liftoff improvements (work in progress)
Merge branch 'master' of https://github.com/FlightDataServices/FlightDataAnalyzer