Add asynchronous prompting support.

A unique token is generated for each prompt, and the prompt request details and callback are cached with this token. The dashboard prompting app responds to prompts using this token, which is then used to call the appropriate callback.

Also rationalised the prompt choices to be the same for all prompt types.

Jira issue: WP-956
Added temporary dashboard widget.

Jira issue: WP-956
Remove redundant code

Jira issue: WP-956
Fixed tests.

Fixed tests to work with asynchronous prompt mechanism.

Also removed redundant references to promptMan module.

Jira issue: WP-956
Integrated prompt UI

Updated prompt widget to use UI

Jira issue: WP-956
Merge pull request #10 from TobyEalden/dashboard-prompting-03

Asynchronous prompting