Create Yeoman generator for PowerShell projects

[daviwil]

Visual Studio Code uses Yeoman for their "File -> New Project" experience, so we need to produce a Yeoman template that can generate a new PowerShell module project. Potentially other project types as well (DSC resource, etc?).

[daviwil]

Have started a new repo for this effort:

http://github.com/PowerShell/generator-powershell

Will file bugs there instead.