action: new bitbake-layer plugin to create a simple layer

action: new bitbake-layer plugin to create a simple layer

Though the script bitbake-layers (from the bitbake project), this plugin
creates a simple layer with a example recipe, the latter with a single task
(do_build). Layer's license and priority is MIT and 6, respectively. Example
recipe and layer's priority can be specified through the command line.

[YOCTO #11567]

Signed-off-by: Leonardo Sandoval <leonardo.sandoval.gonzalez@linux.intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>