* fixed fillSituationsArray to return correct initial situations
* VERIFY ranges and times to avoid inf/NaN and issues in general
* if invalid situations, continue with last situation
* count invalid situations
* return interpolation results parts/situation in one step
* base class init for each interpolation step, less redundant code
* removed old interpolation/parts function
* adjusted unit tests and simulator objects (such as SimObject)
* using interface IInterpolant, renamed to CInterpolant for concrete implmentation
* CInterpolatorPBH has itws own file now, is included
* linear interpolator only re-calculates interpolant when needed (same as spline interpolator)
* interpolators use providers for client/situations/parts/ground elevation
* interpolators do no longer use own situations/parts, but those from provider
* interpolators are no longer QObjects (as it is not needed)
* use gnd flag from situation for gnd interpolation, there is no longer a parts gnd flag interpolation
* guess parts during interpolation
* changed iterators to m_s[i] as it makes clearer which values are used
** the flag is transferred from parts -> situation in airspace monitor
** if the other client already provides and gnd.flag in situation this also works
* adjusted logging
* use providers in unit tests / adjusted tests
* improved situation verification/assert
* all interpolation positions can be logged (3 for spline, 2 for linear)
* interpolated (log) time, setting to real time (i.e. unadjusted time)
* only set logger values with logger attached
* only interpolant needs those values
* encapsulated in struct PosArray
* Interpolant needs no reference to interpolator (anymore)
* const CInterpolatorPbh &pbh()
