Add value comparison operators

Add Ops:
    * Equals (==)
    * Not Equals (!=)
    * Greater Than (>)
    * Less Than (<)
    * Greater Than or Equal To (>=)
    * Less Than or Equal To (<=)

Sort op keys in reverse order to assure longer keys are processed before
similar but shorter ones. This is the case with "<" and "<=": we want "<="
to be processed first otherwise, it assumes "<". Since dictionary keys are
non-deterministic, this is necessary.

Bumped coverage minimum to 60%