Calculates the Quantisation Error, defined as the average distance between and input data vector and the
weight-vector of its best-matching-unit.
Calculates the following values:
Quantisation error (qe).
Visualization of some aspects of Quantization Error
Notes: Only the measures relating to the Units will be drawn (Unit_QE, Unit_MQE)
does not need input vector, data is stored already in unit file
computations of both methods is very similar, should be combined