Gaussian and Exponential numerical codes are inverted for random source simulation

[ronanpaixao]

Lines 560 and 562 are inverted in HighLevelElement.py (reference).

According to the documentation itself in line 525, the code for a gaussian distribution is 2 and for exponential is 3, but they are inverted in code.

TL;DR:
Actual code using a gaussian random voltage source showed the bug, by generating only positive voltages, which is true for exponential distribution but false for gaussian distribution.