UI Accessibility Improvements: Error (and success) messages are displayed above the page heading and all content, unapparent to screenreaders

Problem:
Rather than sending focus to (and reading) the success message, focus stays at the
action button (for example, at the “Add” button for the Add member process).
○ The screen readers users did not even know to look for the messages without the prompting of a sighted observer. Instead, they had to assume the requested action was completed.
○ Magnifier users did not see the messages because the colored bar appeared above the field of magnification and the text appeared too far to the left of the field of magnification.