webui-vue: Add a task to find node licences

Many open source licenses require the module and license to be
identified in the image.  Yocto provides this capability for the
modules that it includes; however, this doesn't cover the modules
that npm includes during the build of webui-vue.

This change adds a new module named 'nlf' to find and create a summary
of the nodes and their licenses.  The nlf recipe file was generated
automatically with:
devtool add 'npm://registry.npmjs.org;package=nlf;version=latest

'

Then a new 'find_node_licenses' task in the webui-vue recipe uses
'nlf-native' to create a summary and save it to the webui-vue license
directory where Yocto stores its license info.

Tested:
Confirmed that the nlf recipe builds.

Confirmed that the 'find_node_licenses' task runs and that the
license summary is available under
'build/tmp/deploy/licenses/webui-vue/node-licenses'

Change-Id: Ia53f6e463db6966f450be2a37dc82a3c5e3f76c1
Signed-off-by: Jason M. Bills <jason.m.bills@linux.intel.com>