WyCS: Added tests cases to show need for GCD
Currently, polynomial terms are not normalised using GCD, and this is a
significant limitation which (amongst other things) leads to infinite
loops in the application of inequality inference.  Therefore, I've added
several test cases which demonstrate the need for this normalisation.
WyCS: Added rule for polynomial normalisation via GCD.
This should prevent the problem of infinite loops of inequalities
building up, although it is not a cheap rule.  Currently, unfortunately,
no more test cases are passing.  Some bugs to iron out still.  #393