Update build to clear node modules directory (PowerShell#1741)

* Update build to clear node modules

Add removal of the node_modules directory on Clean task.

Move condition for restore to the build prerequisite.

This allows the restoring of node modules even if the folder exists.

* Don't remove node_modules.
This causes bad things to happen when you're editing in vscode
(@types is locked until code exits)
Next best thing might be to npm prune (or maybe npm install?)

* npm install keeps putting these spaces in...

Author: corbob

package.json

@@ -503,8 +503,8 @@
           "description": "Specifies the visibility of the Command Explorer in the PowerShell Side Bar."
         },
         "powershell.sideBar.CommandExplorerExcludeFilter": {
-          "type":"array",
-          "default":[],
+          "type": "array",
+          "default": [],
           "description": "Specify array of Modules to exclude from Command Explorer listing."
         },
         "powershell.powerShellExePath": {

vscode-powershell.build.ps1

@@ -57,9 +57,9 @@ task ResolveEditorServicesPath -Before CleanEditorServices, BuildEditorServices
     }
 }
 
-task Restore RestoreNodeModules -Before Build
+task Restore RestoreNodeModules -Before Build -If { -not (Test-Path "$PSScriptRoot/node_modules") }
 
-task RestoreNodeModules -If { -not (Test-Path "$PSScriptRoot/node_modules") } {
+task RestoreNodeModules {
 
     Write-Host "`n### Restoring vscode-powershell dependencies`n" -ForegroundColor Green
 
@@ -73,6 +73,7 @@ task Clean {
     Write-Host "`n### Cleaning vscode-powershell`n" -ForegroundColor Green
     Remove-Item .\modules\* -Exclude "README.md" -Recurse -Force -ErrorAction Ignore
     Remove-Item .\out -Recurse -Force -ErrorAction Ignore
+    exec { & npm prune }
 }
 
 task CleanEditorServices {