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 '$var' at the time of interpolation.
Interesting... we already have a few string formatting/interpolation schemes in Dart-land. I wonder if syntax and or implementation can be borrowed. Built-in we have `'$x'` and `'${formatDate(x)}'`. PolymerExpressions, Angular and Mustache use `'{{x}}'`, and PolymerExpressions allows formatting via filters like `'{{ x | formatDate }}'`. UriTemplates (https://github.com/google/uri.dart) use single curlies and have some built-in operations for lists, maps, etc.

We also have things like NumberFormat in intl https://api.dartlang.org/apidocs/channels/stable/dartdoc-viewer/intl/intl.NumberFormat

It'd be nice to play nice with other existing solutions in Dart. Let's discuss this in an issue.