Create separate Top-level directory per platform

- Replace src\powershell top level project by two
  new root-level projects:
    - src\powershell-unix
    - src\powershell-windows
- Break src\Modules into more granular structure:
  - Shared
  - Windows+Unix-Core
  - Windows-Core
  - Windows-Core+Full
  - Windows-Full
  - To be created: Unix-Core. We will do it as a separate PR
- Fix #1122 : Platform-specific set of Modules (and assemblies)
- Fix Start-TypeGen to work with new top level folders layout

test/csharp/project.json

@@ -2,7 +2,6 @@
     "name": "powershell-tests",
     "version": "1.0.0-*",
     "description": "PowerShell On Linux xUnit Tests",
-    "authors": [ "andschwa" ],
 
     "buildOptions": {
         "keyFile": "../../src/signing/visualstudiopublic.snk",
@@ -11,7 +10,7 @@
     },
 
     "dependencies": {
-        "powershell": "1.0.0-*"
+        "System.Management.Automation": "1.0.0-*"
     },
 
     "frameworks": {