Add build canceling

[TCDooM]

Build Canceling/Stopping POST the <buildCancelRequest comment='CommentText' readdIntoQueue='true' /> item to the URL of a running or queued build. Example of cancelling a running build: click to expand Note: Readding of builds into the queue is supported for running builds only. Example of cancelling a queued build: click to expand Expose cancelled build details: See the canceledInfo element of the build item (available via GET http://teamcity:8111/httpAuth/app/rest/builds/)