* archive: fix unrar check when using unrar-free
unrar-free returns the error code 1 when run without arguments, thus
failing the presence check. Replacing the current presence check with
(( $+commands[unrar] )) fixes the problem.
* archive: add unar support for lsarchive and unarchive
No `archive` support with unar.
Nicola Corna
Jeff Widman
Matt Hamilton
Khai Do
Sorin Ionescu
nasenatmer