- Post-argument subcommands are subcommand which appear after the argument of their parent commands, and accept those arguments in their method hooks
- Internal rewrite to the tab completer code, since it was old and messy. It is now somewhat faster, much cleaner, and will suggest tab completion options with spaces in quotation marks even if you have not typed a quotation mark
- Added `postarg` tag to the command parser for defining post-argument subcommands