git related improvements and implementations

+ Get-GitRepo - Clone or update a repo, with tag support
+ Get-GitHubReleaseTag - Grab tag from latest release page
+ Refresh-GitRepo - Stage all possible changes, discarding any
previously stageds changes
= GitHub repo is now git repo - as some code isn't GitHub specific
+ cat Alias for Get-Content
= Get-PossiblArguments improvement
= Invoke-WebDownload fix
= dcedit fixing bad argument processing

base/Invoke-WebDownload.ps1

@@ -33,7 +33,7 @@ process {
     $outputFileName = Join-Path $OutputPath $outputFileName
 
    if( (Test-Path $outputFileName) -and -not $Force) {
-        throw "$OutputPath already exists"
+        throw "$OutputFileName file already exists"
     }
 
     Write-Verbose "About to start download from:`n`t$Url`n`tto`n`t$outputFileName`n"