Generalise `no_arg_parser` in `command_parser` in CLI

[gburd]

Currently each command that takes no args has it's own separate parser. This ought to be able to be generalised. My idea was:

• Amend no_arg_parser to take a command
• Move the keyword matching and map from specific parser to no_arg_parser
• Use command type to determine which keywords should be matched for this command type
• return that command type inside the map.
• Use no_arg_parser inside choice instead of close_parser, exit_parser and schema_parser.