Update the developer documentation with information about the pipeline whitelist feature.
Update the developer documentation with information about the pipeline whitelist feature.

Signed-off-by: Kam Leung <bbd6ea552864be24bc8b0a608253fbbecfbc9c10@pivotal.io>

gocd/developer.go.cd,gocd/developer.go.cd,gocd/docs.go.cd,gocd/docs.go.cd,ketan/docs.go.cd,ketan/docs.go.cd,gocd/developer.go.cd,ketan/docs.go.cd,gocd/docs.go.cd