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

From now on successful responses are in Hal+Json format.
Tested only by hand, test 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.
Merge branch 'web' of https://github.com/blstream/UrbanGame into web
URBNG-35 Initial version of WebAPI - more commands

Changes:
* Added "join game" command
* Added "leave game" command
* Added "get list of tasks" command
* Added "get task static data" command
* Added "get task dynamic data" command

Still, response information are useless because of very simple game
service mock. Only response format matters (Hal+Json).

Tested only by hand, in web browser.
Merge pull request #66 from mkaim/web

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