Remove the need for external dependencies
Allow certain commands to be hidden

Handlers marked as hidden will not be visible on any help views
(essentially invisible to the user).
Assign a default value for the Accept annotation
Add an in-built UUID converter
Rename getReadable...() -> getAccepted...() for string syntax
Refactor classes related to the BukkitRegistry
Vastly improve command sorting (and therefore execution priority)
Properly account for unbound ('loose') converters
Improve syntax matching and argument consumption
Reduce suffix for help page header
Append any characters in between matches
Add various new test commands
Minor formatting improvements