OpenCore 0.6.8

First release available! No more cloning!

• Updated from OpenCore 0.6.7 to OpenCore 0.6.8
• Updated kexts
• Changed from alcid=20 to layout-id=0D000000, as recommended in OpenCore's guide
• Added documentation on how to update
• Changed from the OpenCorePkg's Resources folder to the one from OcBinaryData, so as to avoid problems with OpenCanopy when updating
• Removed the Resources/Audio folder, since is not being used (if you need it to add boot chime, then just download and use that folder)
• Improvements in README.md