devtool: add package plugin that lets you create package via devtool
Enables creating packages using devtool within the extensible SDK. (This
is only enabled within the extensible SDK because it provides no
advantage over just running bitbake directly there).
Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com> Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
