Noise simulation

Shaper

• Store the shaper type as an enum instead of a string.
• Fixed a typo in the transfer function formula for the bipolar shaper.
• Precompute prefactors and integrals.
• Use analytical expressions for the integral of the transfer function squared.
• Moved the sampling of the noise in each bin from Shaper to Sensor.

Random

• Added a function (RndmPoisson) to draw Poisson-distributed random variates.

Sensor

• Added a function (SetSignal) to set the signal in a given bin explicitly.
• White noise can now be simulated either
  • by sampling the number of noise delta pulses in the time window from a Poisson distribution, distributing these pulses randomly over the bins, and subtracting the mean, or
  • by sampling the noise charge in each bin from a Gaussian distribution.