Add demo utility functions to the UI component

[niallthomson]

Establish an initial set of utility functions in the UI component to enable demonstrations. The podinfo application provides lots of these.

Suggested functions:

• GET /headers Print the heads of the inbound request
• GET /status/{code} Return the given HTTP status code
• GET /panic Shutdown the application with an error code
• POST /echo Write back the payload sent to it
• POST /store Write the payload to a file and return a hash
• GET /store/{hash} Return the payload from the file system previously stored

[vijayjeevarajaws]

I can work on this.