String Additions

String capitalization. Index-based insertion, replacement, and removal. Similar implementation of C# String.Format(..) to allow for terse index-based string interpolation without needing to use a literal with '$var' at the time of interpolation.
It's nice to have the invariable argument size but it's more of a gimmick and works just as well to encapsulate the method call into a list, I'll remove it in my next commit.