Reverse Thrust Asymmetry, Ground Track and Peak Curvature

ThrustAsymmetryWithReverseThrustMax algorithm now uses clump_multistate
as tidier implementation. Ground Track Precise function handles missing
straight_ends properly, and Peak Curvature algorithm handles void
calling state.
blend_two_parameters now works with integers

Data that converts to integer formats was being wrongly handled by blend
two parameters function due to python integer arithmetic. We may
implement a policy to force all converted parameters into float format,
but this is a "belt and braces" correction and test.