Add 'Parallel' switch to Invoke-PSDeploy

[RamblingCookieMonster]

In some cases, deployments may benefit from running in parallel. It might help to add a 'parallel' switch that invokes deployments in parallel via runspaces.

This may be as simple as inserting runspace handling for this loop in Invoke-PSDeploy

I'm game for any implementation. Depending on PoshRsJob, adding a small handler (e.g. Invoke-Parallel, but maybe stripped down), or even our own handling.

Cheers!