kamiftp: implement ‘rm’ command

kamiftp: implement shell-like word splitting way more useful than a dumb strsep(" ")

kamiftp: ls: accept an optional a path

kamiftp: accept an optional 9p:// prefix in the connstring

kamiftp: deprecate -c it's useless as -C already implies it and -C must be use when connecting with TLS. To be definitely removed after 0.3.

kamiftp: add -o to chose the path where to save the named file

kamiftp: automatic cd or fetch on the given path before the given path was used for Tattach. Turns out at least u9fs doesn't seem to use that field for the initial directory (not sure if it should). kamiftp now always issues a Tattach with aname="/" and then does a Twalk on the path: if it names a directory, it becomes the remote working directory like a `cd' was issued, if it names a file it is fetched and kamiftp quits.

kamiftp: use the [user@]host[:port][/path] syntax instead of taking the path as a separate argument. For some time the old style will be supported.

add blank before comma, reported by man -Tlint

kamiftp.1: specify how USER is used

ftp: allow user@host syntax; guard against empty user or port

specify that the syntax for the host optionally accepts a port number

make -C and -K imply -c

simplify -c phrasing

update manpage