devtool: add: figure out recipe name from recipetool

devtool: add: figure out recipe name from recipetool

recipetool create now has all the logic in it for auto-detecting the
name and version, and using those in the file name - so we can make the
name an optional parameter for devtool add and we pick up the file name
that recipetool has used after the fact.

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>