Add DistributedVirtualPortgroup wrapper
Fix default network in NetworkFlag

Switch to higher-level govmomi types and use their Name() method,
rather than flag.name which is only set when -net flag is given.
Merge pull request #111 from dougm/dvs

Fix default network in NetworkFlag
Merge pull request #112 from dougm/esxcli

Handle empty values in esxcli
Add esxcli related types and methods

From the internal vmodl
Refactor unmarshal
Refactor esxcli to esxcli.Executor