[common] JsonFilter prototype implementation.

[common] JsonFilter prototype implementation.

In present WebAPI implementation, several modules implement their own
data filtering algorithms. This commit is an attempt to provide a common,
unified way to perform data filtering across entire API.

Design goal for this change was simplicity. I was not looking for ways
to optimize the performance, as this will require in-depth performance
testing in specific use cases.

[Verification] Unit tests for JsonFilter class has been implemented which validate
main logic.

Signed-off-by: Michal Michalski <m.michalski2@partner.samsung.com>
Change-Id: I6cfb9fc98f6a1be8d6364a9dfff2bf07ba239dfa