KITCHEN-68 add basic network options
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[KITCHEN-68] Convert :forward_port and :network to be arrays.

Since forward_port statements are allowed multiple times, it makes sense
to permit this as well. Same with network statement.

Now a user can set multiple forward_port statements with:

    driver_config:
      forward_port:
      - [80, 8080]
      - [443, 8443]

and multiple network statments with:

    driver_config:
      network:
      - [hostonly, 192.168.33.10]
      - [bridged]

References #1
Merge branch 'KITCHEN-68'