Introduce changes to generate metadata artifacts

[sabbyanandan]

As a developer, I'd like to create a JAR artifact for each task app-starter, so I embed the application metadata and the whitelisted properties in it.

Acceptance:

• the JAR artifact is automatically generated at the build time
• the companion artifact can be used by other clients such as SCDF's shell, dsl and UI
• unit-tests verify the creation and existence of the companion artifact for each task app-starter

[sobychacko]

This is completed.