refactor(bash/ebuild.lib): remove duplicates from var filter list

Specifically PKGCORE_DOMAIN is covered by the PKGCORE_.* glob and
BASHOPTS is covered by the BASH.* glob.
refactor(bash): more bash consistency changes
feat(pmaint): add --verbose option to `pmaint regen`
feat(pmaint): add --rsync option to `pmaint regen`

Currently this just updates metadata/timestamp.chk when metadata
regeneration occurs.