This PR makes it easy to generate and execute testcases for VM arithmetic operations. By enabling and running the testcase TestWriteExpectedValues, a set of json files are created which contain input and output for each arith operation.
The test TestJsonTestcases executes all of those tests.

While meaningless as is, this PR makes it less risky to make changes (optimizations) to the vm operations, since there will be a larger body of testcases.