testutilities: Add new randomizer functions

Generate single random number from time + wrap
time sincce epoch calculation into new function.
testutilities: RandomMatrix() uses epoch-function

Shorten code by using the SecondsSinceEpoch()
function.
testutilities: Add RandomVector() functions

These functions create whole vectors filled with
random values. They are better to use than x-
times Random() alone, it's faster and the
random values are more random (doesn't initialize
the generator everytime).
math/linear_function: Add test suite

Add test suite for LinearFunction object.