[Feature Request] Followup tasks on the generic gas meter

[vgao1996]

https://github.com/move-language/move/pull/281 implements a generic gas meter and there are some tasks we identified but chose to do later:

1. Safe Gas Algebra a. Right now gas operations are unchecked, meaning that they could suffer from arithmetic errors like overflow or div by 0. b. We have a GasAlgebra trait, but sadly it also uses unchecked arithmetic
2. GasStatus a. We'll need to decide what to do with this: i. Move it to a different location? ii. Simplify/rewrite it? iii. Remove it?
3. Fix move-cli