603 Allow an App to retrieve its own metadata through getInfo()

[kriswest]

resolves #603

As agreed at #683 this PR adds the calling app's AppMetadata to the ImplementationMetadata returned by fdc3.getInfo(), allowing an app to know its own own appId and instanceId without adding new functions to the desktop agent API.

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[nkolba]

@kriswest - curious about what an app might do with its own instanceId (or appId - if it didn't already know it).

[kriswest]

@nkolba see commentary on the issue: #603 (comment)

It basically stems from the fact that an app doesn't necessarily know its own metadata (particularly if added to an appD that the author doesn't control) and can more easily discover the metadata of other apps than it can it's own. This change provides that metadata, allowing it to do things like spawning a copy of itself, recognizing its own metadata, differentiating itself from other instances (e.g. after calling findInstances), adding its details to log messages to enable better debugging etc.. These are not major use cases, but they have merit and I/we expect to find more of them in future.