Port math related methods to MathUtility

[meganindya]

I've moved the math related methods from Logo to MathUtility in a new file utils/mathutils.js. I've actually created the class MathUtility, and all methods are static.

I've refactored the arg methods corresponding to the 10 methods that I moved, in a way that arg methods handle only activity specific to blocks, while the static methods verify the input and produce results accordingly. I've used exception handling to communicate between the two disconnected operations.

[walterbender]

Looks good but could you rebase so that your previous commit is not also folded in to this PR? Thx

[meganindya]

Yeah, I just did that. logo-refactor-1 is 2 commits ahead now. But, it doesn't show here.

[meganindya]

A soft-reset followed by a force push fixed this :p