Support building extension using CI services

[jcfr]

Similarly to what is done with ITK, the Slicer build tree could be archived daily. Then, it would and be available for download so that extension maintainers can setup independent build and test using AppVeyor, CircleCI and TravisCI.

• https://github.com/InsightSoftwareConsortium/ITKModuleTemplate
• *-download-cache-and-build-module-wheels scripts: manylinux, macOS, windows,
• *-build-tarball scripts: manylinux, macOS, windows

See #1557

from @pieper :

@sjh26 and I were discussing this in the context of this issue where the s4ext file pointed to a git hash that didn't even have a CMakeLists.txt file, but the log
info was only on the factory machine. If we tried to build the extension as part of CI then the extension
contributor would be able to investigate independently.