Allow defining a PSDrive to child location

[jdhitsolutions]

In much the same way that the Registry provider allows me to map a PSDrive to a specific registry key, I'd like to be able to map a CIM psdrive like this:

new-psdrive cimv2 -PSProvider SHiPS -Root cim:\localhost\cimv2

As of version 0.3.0 this is not allowed. Although I recognize, this may be a SHiPS issue.