Improve message output for users list

Also removes double/unneeded spaces.
Merge pull request #1376 from stuntguy3000/patch-1

Improve message output for users list
Fix load call for options. Fixes #1382
Actually bump version for 1.21.1 dev
Fix exception handling of permissions backend errors
Just make PEX begin migrating prefixes (actual migration coming in the future)
Implement BukkitDev-compatible autoupdater. Fixes #1384

Also perform pom cleanup
Add additional verification of jdk1.6 compatibility
Cleanup default methods
Fix handling of not-inheritable permissions. Fixes #1386
Fix handling of default groups for null world
Bump Bukkit dependency to 1.7.8
Add command to bulk-convert users to UUID now that Bukkit's OfflinePlayer objects are more likely to return a valid uuid
Modify autoupdater to only update between bugfix releases
Release version 1.21
Prepare for development on 1.21.2
Fix issue with certain option configurations breaking prefixes and suffixes
Restore sqlite compatibility
Fix isVirtual checks for permissions entities
Prevent both old-style and new-style prefix entries from existing