standardize unarchive step for zips

move all unarchiver processor runs into download recipe for products
distributed in zip format, as both munki and pkg recipes rely on that
step anyway, reducing recipe length overall.
Unneeded/unused processor steps in Reflector.munki

Clear out unnecessary unarchive and dmg creation steps for Reflector,
since it’s distributed in a dmg already
Merge branch 'move-unarchive-to-download'