If no directory was passed by the user as an explicit option and there is a folder named "magefolder" use that.

Workdir is kept as it is likely still "."

Also correct os.Stat error checking to expect no error

Magefolder was renamed to magefiles
We now accept files that are not tagged too when using a magefiles directory

When using magefiles directory, if there are mixed tagging files assume tagging is used for mage files

We support building for older go versions so error formatting should use %v

When mixed tagging is found within a magefiles folder, opt to use all files

…racio/add_magefolder

Add a temporary preference for mage files over magefiles directories and warn users this is a temporary functionality leading to a change where directory will be preferred.