Flare DMG creator

Thanks to @tvleavitt for Flare DMG Build Documentation.pdf

To use these scripts you should have packaged flare using flare-engine/package_osx.sh.

Note DMG packaging on Apple is a mess, I did not listen to the advice on stackoverflow:

• "Don't go there. As a long term Mac developer, I can assure you, no solution is really working well."

So here be dragons

• For dmgbuild-flare.sh you will need pip install dmgbuild but there is issues with dmgbuild and python3 so a fork was needed.
• For create-dmg-flare.sh you will need brew install create-dmg, but there is issues with icon generation.