Multiple swarms

[michaelPf85]

Working on #90 Currently the plugin seems to consider the Docker Swarm cloud as a singleton, so there are several places in the code that would need to be changed to work with a list of items, instead of a single default one.

• ApiRequest changed to take SwarmName as a parameter, to get both Docker host URI and configured CredentialsId
• Only PingRequest does not provide a SwarmName, since it is used before saving the configuration
• DockerSwarmCloud.get() has been changed to take a swarm name parameter, so all code relying on this singleton has been modified to handle multiple swarms
• Code managing dynamic nodes has been changed too, and needs some cleanup
• The dashboard page kind of works but only displays the first swarm found, for now

[emilsniadach]

Hi Michael, do you have this review rebased to latest plugin version and compiled ? I'm interrested in this feature as we would like to have multiple swarm in Jenkins.