added vm query VMNAME QUERY sub-command

This commit adds a new sub-command to query the named VirtualMachine properties.  Any method exposed by http://pubs.vmware.com/vi3/sdk/ReferenceGuide/vim.VirtualMachine.html is supported.

Examples:
% knife vsphere vm query myvm network[0].name
Development Network

% knife vsphere vm query guest.ipAddress network[0].name
10.0.0.55