added commutative tests for node-probability method
implemented 1st half of variable elimination algorithm (sum-out)
code cleanup / removed comments
changed floats to double floats for better precision
cleaned up code
sum-out can eliminate a list of nodes now.
taking in consideration the trivial result of sum-out, that you get when you sum out all vars
added a Test for sum-out function
added test for assertion failure
renamed function, because it can sum-out more than one var now
moved code of CPT creation to own method, to reuse it as needed. Started to implement product of CPTs
implemented factor-product