rkt: merge global flags into command flags

This is a dumb strawman hack to make working with global args a little less fussy, e.g. now you can do
	`rkt run -debug ...`
instead of always having to remember
	`rkt -debug run ...`

It also means that all the global args show up in the --help for subcommands
can we add a comment at line 28 "all the global flags will be merged into subcommand"?