fixed #139:  unzip for Windows Server Core environment

This is fixed at least if using powershell v3+ with .net 4.5. With this the test for powershell v3+ are executable on AppVeyor (see [![Build status](https://ci.appveyor.com/api/projects/status/67nseiet6m3fxkin)](https://ci.appveyor.com/project/flofreud/psget)). To execute the test for v2 in Windows Server Core environment a different unzip solution would be necessary.

Changes of this PR:
- .net-based implementation of Expand-ZipModule is default if .net 4.5 is available in powershell v3+
- otherwise the com-based implementation is used
- throws an error if nothing was extracted and no error occurs.

#139 fixed and v2-tests also running