class HRungeKutta

 clears magnetic field definition and vertex position and direction

 sets the field map and the scaling factor

 sets the MDC module position in the sector coordinate system
 calculates the normal vector on the planes

 Input:  position and direction of the two segments u1 and u2,
         array with multiplication factors for errors
         sector number, initial guess for momentum
 From the segments the hit positions are calculated.
 Calls fitMdc for Runge-Kutta track propagation and fitting

 Input:  position and direction of the two segments u1 and u2
         array with multiplication factors for errors
         sector number, initial guess for momentum
 From the segments the hit positions are calculated.
 If the multiplication factors for errors of a hit -1, the hit is discarded.
 Calls fitMdc for Runge-Kutta track propagation and fitting

 calculates the hit points in the MDC module (index mdcN 0..3)
 input:  posline == pos from track piece
 input:  dirline == pos from segment
         mdcN    == module number 0..3
 output: xyz     == hit position in module

 Here we set initial approximation momentum value

 calculates the distance between two points

 RK propagation with initial or last fit parameters
 uv - vertical direction in MDC1
 uh - horizontal direction

 calculates the derivatives (RK propagation with parameter variations)
 uv - vertical direction
 uh - horizontal direction in MDC1

 calculates the direction

 calculates the derivative (hit-fit)/variation

 solves the system of linear equations and sets the new fitting parameters

 propages the track through the MDC system
 p      == momentum
 upos   == initial position
 udir   == initial direction
 hitxyz == hits in chambers
 kind   == type of variation

 one step of track tracing from the position upos in the direction of udir

 calculates 2nd derivative

 propogates the track backwards from first MDC till Z=zVertex plane
 should be called only after RK-minimisation is done

 propagates the track from the last fitted MDC position till track intersection
 with META plane (is defined by META-hit and normal vector to rod's plane
 should be called only after RK-minimisation is done

 upos, udir - "moving point" current position and movement direction vector
 planeR0[3] some point on the plane to which intersection is supposed to happen
 planeNorm[3] perpendicular vector to the plane
 pointIntersect[3] - output - the intersection point of "moving point" with plane

 THis part is copid from ROOT TDecompLU::Decompose() to get
 rid of error message!
 Crout/Doolittle algorithm of LU decomposing a square matrix, with implicit partial
 pivoting.  The decomposition is stored in fLU: U is explicit in the upper triag
 and L is in multiplier form in the subdiagionals .
 Row permutations are mapped out in fIndex. fSign, used for calculating the
 determinant, is +/- 1 for even/odd row permutations. .

 fitted points on MDC in Segment Coord System, Mdc={1,2,3,4}

 hit points on MDC (from segments) in Segment Coord System, Mdc={1,2,3,4}

 difference between of fitted points and hit points

 position and direction on first MDC after RungeKutta fit

 position and direction on last MDC after RungeKutta fit

 position and direction on META after RungeKutta fit