Adding knife wsman test to validate WSMAN/WinRM availability

This adds a command "knife wsman test" to help verify connectivity to remote WinRM endpoints.  Currently this can be tested from Windows nodes with PowerShell, but it is more difficult to validate connectivity cross platform.  This command will validate that the remote port is reachable and listening for management requests similar to Test-Wsman in PowerShell. 

Targets can be specified manually (as per the knife winrm command) or use search to identify target nodes.
I'm not sure on the latest style guidelines around nesting classes -- my instinct would be to add this to a separate source file and just require it from here -- that way it is pretty easy to keep track of the unit tests for the class for instance.