Separate the act of adding and starting a job

Separate the act of adding and starting a job

CMD_JOB or CMD_JOB_LINE only adds the necessary jobs, which will
automatically return the job option info to the client. Let the
client do what it wants with the options, then have the client
send a CMD_RUN command to actually start the jobs.

Next we'll have a command for passing back edited options, so that
the client can update existing options.

This adds a new button to gfio, to note this split of add and run
as well.

Signed-off-by: Jens Axboe <axboe@kernel.dk>