(GH-1311) Install-ChocolateyPowershellCommand File/FileFullPath aliases

Allow using File / FileFullPath aliases with PsFileFullPath as they are
well-known aliases and it brings consistency across different commands.

src/chocolatey.resources/helpers/functions/Install-ChocolateyPowershellCommand.ps1

@@ -49,11 +49,13 @@ Full file path to PowerShell file to turn into a command. If embedding
 it in the package next to the install script, the path will be like
 `"$(Split-Path -parent $MyInvocation.MyCommand.Definition)\\Script.ps1"`
 
+In 0.10.6+, `File` and `FileFullPath` are aliases for PsFileFullPath.
+
 .PARAMETER Url
 This is the 32 bit url to download the resource from. This resource can
 be used on 64 bit systems when a package has both a Url and Url64bit
 specified if a user passes `--forceX86`. If there is only a 64 bit url
-available, please remove do not use the parameter (only use Url64bit).
+available, please remove do not use this parameter (only use Url64bit).
 Will fail on 32bit systems if missing or if a user attempts to force
 a 32 bit installation on a 64 bit system.
 
@@ -176,7 +178,7 @@ Install-ChocolateyZipPackage
 #>
 param(
   [parameter(Mandatory=$false, Position=0)][string] $packageName,
-  [parameter(Mandatory=$true, Position=1)][string] $psFileFullPath,
+  [alias("file","fileFullPath")][parameter(Mandatory=$true, Position=1)][string] $psFileFullPath,
   [parameter(Mandatory=$false, Position=2)][string] $url ='',
   [parameter(Mandatory=$false, Position=3)]
   [alias("url64")][string] $url64bit = '',