Add all/none for new enum flags

[christopherzimmerman]

I was quite happy to see added support recently for enum flags in #3025 , I think there are a couple more tweaks that could be made to improve usability.

[flag]
enum TensorFlags {
	contiguous
	fortran
	owndata
	write
}

Many other languages implement all and none for flags, so instead of having to check each flag, being able to do something like:

flags.has(.all)
flags.has(.none)

Would be really nice.

Even nicer would be bitwise operations on flags:

flags &= ~TensorFlags.write

etc.