parseOpts now does some preliminary path screening to prevent
command sequences like

	`ipfs <hash> cat`

from succeeding. The tests affected by this have been slightly altered,
but should be restored once parseOpts is decoupled from path analysis.

Command suggestion printing has also been factored into a single
function.

Fixes: #2501
License: MIT
Signed-off-by: Thomas Gardner <tmg@fastmail.com>