cli: Set worker.build in addition to worker.project
cli: Set worker.build in addition to worker.project

* 'project' allows searching for workers coming from testswarm-browserstack
  (as opposed to those from other users and programs from the same org)
* 'build' allows grouping workers spawned during the same run.

mzgol/testswarm-browserstack,clarkbox/testswarm-browserstack,clarkbox/testswarm-browserstack,mzgol/testswarm-browserstack