devtool: add "rename" subcommand

devtool: add "rename" subcommand

When you run devtool add on a source tree we attempt to figure out the
correct name and version for the recipe. However, despite our best
efforts, sometimes the name and/or version we come up with isn't
correct, and the only way to remedy that up until now was to reset the
recipe, delete the source tree and start again, specifying the name this
time. To avoid this slightly painful procedure, add a "rename"
subcommand that lets you rename the recipe and/or change the version.

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