This introduces two new utility functions for easily constructing and

processing common types of message dialogs:


Ink.showConfirmDialog: Shows a confirmation dialog (a replacement

  for window.confirm().


Ink.showErrorDialog: Shows an error dialog (a replacement

  for window.alert().


These are designed as utility functions that take a minimal set of

options (but can be fairly customized). They return a Promise, which is

resolved only once a choice has been made, allowing an async function to

await on the result and process it before continuing.
If the user confirmed, they'll get a truthy object that contains further

information that may be useful for processing. If they cancel, they'll

get a null result instead.
The confirmation dialog can also take an async onConfirm handler,

which will keep the dialog open and the buttons in a busy state until

completed. That may return false, which will abort the dialog the same

way as if the user hit Cancel. This is intended for error reporting

during an operation.
Confirmation dialogs can also be suppressed, using the new functionality

in DialogView. This is off by default, but can be opted into. It's up

to the caller to handle all confirmation logic.

Tested in Storybook and changes in Review Board.