Fixes PowerShell#4290
Make mac package require 10.12 or newer.
Required that the package is installed to a disk with macOS installed.
The Apple example XML had a background image added as well, so I added a background image:
https://user-images.githubusercontent.com/10873629/33738943-014c9d00-db50-11e7-9628-310ce6427438.png

Add guidance for submitting PR which are not ready to merge, or work in progress (WIP)

…#5654)

Create linux-arm tarball package in our release build.
Also moved the Linux-x64 tarball creation to Ubutntu 14.04, because Start-PSBuild adds additional symbolic link files when running on Red Hat Family distros.
Note that linux-arm can only be built on Ubuntu, so the tar-arm package will also be generated from the Ubuntu 14.04.

* enable win-arm and win-arm64 builds

* fix using arm64 tools for build
fix finding vs2017 dynamically

* change install-powershellremoting.ps1 script to use reg provider rather than reg.exe so that error doesn't show on success
fix formatting issue in cmake.defs

* add check that path being read from config file is valid
address PR feedback

* fix copying of PowerShell.Core.Instrumentation as VS2017 puts it in $HOME/source
address PR feedback

The Linux release build was broken because AppImage,tar,tar-arm in build.json is turned into a string of "AppImage,tar,tar-arm" by docker run. Now it's changed to use switch parameters.