Long custom app name fails to package on Windows

* Long names generate too long paths in packaging directory on windows.
* The default name is long enough to trigger this with a non release (dated) package name.
* Perhaps we should put in a cmake warning/error if the name is too long?
* See: http://slicer.cdash.org/viewBuildError.php?buildid=1821163

Error example:
``` nsis
File: Descending to: "D:/D/P/SC-0-build/Slicer-build/_CPack_Packages/win-amd64/NSIS/SlicerCustomAppTemplate-0.1.0-0000-00-00-win-amd64\lib\SlicerCustomAppTemplate-4.11\qt-scripted-modules\SegmentEditorEffects\SegmentEditorEffects\__pycache__\"

File: failed opening file "D:/D/P/SC-0-build/Slicer-build/_CPack_Packages/win-amd64/NSIS/SlicerCustomAppTemplate-0.1.0-0000-00-00-win-amd64\lib\SlicerCustomAppTemplate-4.11\qt-scripted-modules\SegmentEditorEffects\SegmentEditorEffects\__pycache__\AbstractScriptedSegmentEditorAutoCompleteEffect.cpython-36.pyc"

Error in script "D:/D/P/SC-0-build/Slicer-build/_CPack_Packages/win-amd64/NSIS/project.nsi" on line 639 -- aborting creation process
```

Start by reproducing the Windows packaging failure with a long custom application name and inspect the CMake/CPack packaging configuration implicated by the NSIS error. Determine whether the completed work should prevent overlong paths or provide a CMake diagnostic; done means the intended behavior is verified during packaging.

Written by the indexing model from the issue text.