This allows each interpolant to specify on its own which PBH
interpolator should be used. Currently only the linear PBH interpolator
is available, but another PBH interpolator will be added for velocity.
This removes some protected data from the IInterpolator interface as well,
which conforms to C++ Core Guideline C.113 ("Avoid protected data").
* 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
* only interpolant needs those values
* encapsulated in struct PosArray
* Interpolant needs no reference to interpolator (anymore)
* const CInterpolatorPbh &pbh()
* removed debug messages from interpolator
* added callsign to getInterpolatedParts / getInterpolatedSituation signatures
* config for logging via CInterpolationAndRenderingSetup::addCallsignToLog etc.
