- i18n now falls back to `en` from `en-US` if message translation isn't found
- View now falls back to `en` from `en-US` if file not found
- Default `sourceLanguage` and `language` are now `en`

fixes #1984

Fixes #1965: `Controller::findLayoutFile()` returns incorrect file path when layout name starts with a slash

Need to add ensureBehaviors() to detachBehavior*().

The intent may be to detach behaviors defined in behaviors().
In the original implementation, if these behaviors() are not yet attached, they can not selectively be detached.

Appended newlines to every PHP document that did not have a newline as the last character in the file.