Introduce user friendlier integer parsing system

This is a massive PR.

The new method introduced into StringUtils is the toInteger method which uses regex to remove all invalid numbers from a string, then convert it as required. This is a better change because it allows users to be a little bit more flexible/error resistant to numbers when being inputted.
It's best if you avoid `\d` and go for `0-9` instead since `\d` matches non-English digits.