devtool: add: show recipetool create output

devtool: add: show recipetool create output

When running devtool add, instead of hiding the recipetool create
output, change it so that it's appropriate to show in the devtool
context and show it in real-time. This means that you get status output
such as when a URL is being fetched (though currently no progress
information.) recipetool create now has a hidden --devtool option to
enable this display mode.

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>