Mergeback 0.9.0 Release

Prior to this commit, it was not possible to use the DSC Base Provider
to invoke class-based DSC Resources. DSC `1.1` (the version of DSC used
by Windows PowerShell `5.1`) cannot call `Invoke-DscResource` for class-
based resources by module path, only by module name; further more, the
module containing the DSC Resource _must_ be available in the *system*
level `PSModulePath` environment variable; munging the *process* level
`PSModulePath` does not work.

This commit updates the DSC Base Provider to:

1. Read the `dscmeta_resource_implementation` value from a the Puppet
   Resource API type definition of a resource and inject it into the
   invocable resource definition
2. Add the `munge_psmodulepath` method to return the PowerShell code to
   modify the system-level `PSModulePath` if the invocable resource is
   is implemented as a PowerShell class; if the resource is any other
   implementation it instead returns nil
3. Modify the `invoke_params` method to set the `ModuleName` key to the
   PowerShell module's name instead of the path to the module's manifest
   if the resource is implemented as a PowerShell class
4. Inject the PowerShell code from `munge_psmodulepath` into the output
   from the `ps_script_content` method to ensure it will be called when
   invoking the resource
5. Update the try/catch in the postscript code file to have a `finally`
   block which resets the `PSModulePath` if it was munged earlier in the
   invocation script, regardless of whether or not the invocation errors

…s-based-resources

(GH-172) Enable use of class-based DSC Resources by munging PSModulePath

(MAINT) Prep for 0.10.0 release