Make the docker widget's sock-path an Array

[ralphocdol]

Description

Having multiple docker servers would require me to make multiple widget of docker-containers, although that's good and all but when I need them to appear in a single tab instead of multiple would not be possible at the moment since each widget will be treated as 1 tab. Turning sock-path property into a list of sock-path would most likely solve this.

- type: docker-containers
  title: Docker
  cache: 1s
  sock-path: 
    - http://docker-proxy1.domain
    - http://docker-proxy2.domain
#....

Though I'd imagine that this would create complexity to the widget if for example one of the socket proxy is down.