simple networks support

You can specify either a network UUID or network name.
Missing or misspelled networks will be ignored.
When provider.networks is not given, vagrant-tiktalik falls back
to default behavior of choosing a first available public network.

config.vm.provider :tiktalik do |provider, override|
       provider.networks = [
          [network name],
	  [network uuid1],
          [network uuid2],
       ]
end