Support reconfiguring a templated VM during deployment

[nhunsperger]

It is common practice to deploy a VM image under multiple labels with different hardware capabilities, such that jobs can use an appropriately sized VM. In order to do so with this plugin, it was previously necessary to maintain multiple vSphere templates.

This commit adapts the existing ReconfigureStep pipeline support for use with templated VMs. It is now possible to modify the VM (CPU, memory, etc) when defining the template. Each VM launched is appropriately reconfigured before being brought online.