Add InvertTest parameter

[briantist]

For some resources, the language of the command is more natural if the result of the test method is inverted.

For example with xPendingReboot, converted with Idempotion:

if (Test-xPendingReboot) { }

It feels like that should be $true if there is a pending reboot, but it's the opposite (because in the case of the DSC resource we want to run set if there is a pending reboot)'.

I envision an -InvertTest switch parameter on Convert-DscResourceToFunction which would translate to a new definition variable to be used (or ignored) by the template definition.