The SDK path can now be overridden by a ARMSDK environment variable which is particularly useful when running Armory/Blender from the command line (thanks @tong for the idea!).
armory.py is now always copied instead of symlinked to prevent invalid installations when the SDK is removed. However symlinking is still available as a developer option because in some cases it can result in less restarting of Blender (if Blender was closed while the changes were made, armory.py is already up-to-date).
If the SDK is not used from the path set in the preferences, but is instead used locally from the project or set by the ARMSDK var, a little hint is displayed in the preferences:
This PR implements a few ideas from https://github.com/armory3d/armsdk/issues/31:
ARMSDKenvironment variable which is particularly useful when running Armory/Blender from the command line (thanks @tong for the idea!).