Remove thread capture

ThinWire has the ability to block execution when a Dialog is visible. This happens by blocking the EventProcessor thread on the server until the Dialog is dismissed in the browser.

Blocking dialogs are generally not done in modern user interface, and the benefits are far out-weighed by the complexity it introduces to the framework. Most of the functionality can be achieved by attaching a callback that executed when the dialog is dismissed.

Because of these reasons, this feature should be removed from the framework.

This request:
- removes the captureThread logic from the EventProcessor
- removes Dialog's waitForWindow property
- removes the Dialog method of FileChooser
- modifies MessageBox.confirm to use a callback