Start the ArrayContext.
Start implementing ArrayContext and some tests.
Build remaining methods on ArrayContext.
Add error() and hasError()

These are important features for generating validation messages.
Doc block fixes.
Renamed View/Input to View/Widget
Renamed InputInterface to WidgetInterface
Make phpcs build a bit faster.
Merge pull request #2754 from markstory/3.0-form-context

3.0 form context
Merge pull request #2758 from ADmad/3.0-widget

3.0 widget