Add build canceling

[TCDooM]

Build Canceling/Stopping
POST the 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/)