URBNG-35 Initial version of WebAPI - Hal+Json format

From now on successful responses are in Hal+Json format.
Tested only by hand, unit tests will be written as soon as
possible.

Comments:
* response "Content-Type" header is not equal "application/hal+json" but "application/json" just for testing in web browser.
* informations in request are still useless, only format matters
* commands connected with tasks (like "get tasks list", "get tasks info", "get task status") are not implemented yet.