zfs comments need cleaner, more consistent style
Various areas of ZFS have style issues, e.g.:
- Lack of (or too much) whitespace in areas
- Bad spelling
- Dense comments that would be easier to read as a list
- Tabs where spaces are more appropriate
- Useless/redundant text
This is more of an ongoing issue, but the end goal is to improve code readability for developers new to ZFS and those returning from working elsewhere.