New-NuGetPackage.ps1 v1.5.11

• Better error handling and messages when determining the path to TF.exe for Visual Studio 2017+.

New-NuGetPackage.ps1 v1.5.10

• Add parameter to allow TF.exe path to be specified.
• Automatically retrieve TF.exe path for Visual Studio 2017+.
• Write warning when TF.exe cannot be found.