Add a Token Generation Page for Acquiring JWT Tokens for integration

This patch provides a new Token Generation application that can be hosted in any topology just as any Knox application. It will be added to the homepage.xml topology initially.

In addition, this application requires the KnoxToken service to be added to the same topology for acquiring tokens.

It also allows the user to select a lifespan for the JWT token in days.
This requires a change to the KnoxToken service itself to accept a lifespan query param.
The requested lifespan must be less than or equal to the configured TTL for the KnoxService.