Drop "zpool28fix" flag. Set to "true" by default.

This does not, however, cleanup the logic as a result. Bit wins could
happen with that, but touches a lot of code that will be refactored
later anyways.
Use getopts to parse script options

getopts is POSIX compliant and surprisingly portable; even SVR4 supports it.
Simplify "prefixes" join; avoid sed call.
Convert Note(), Warn(), et al to printf
Remove $zero_seconds. Move calls to where they're used.
Simplify SkipPool logic

Further paving the way to combine both getopts sections
Merge "generic options" and "pool options"