[CB-3798] Provide support for optional localized binaries[node/npm/bbtools]

-several script updates to provide support for optional localized binaries [node/npm/bbtools]
-Added support for overridable global CORDOVA_NODE env variable to point to node installation
-Added support for overridable global CORDOVA_BBTOOLS env variable to point to bbndk tools
-run plugman via JS and not command-line

Opening for visibility. Still work in progress.

When testing test all regular scenarios as usual and then test again without node/npm/bbtools on your path. Both should work. When testing the second scenario, a dependencies folder must be setup and placed in the *repo*/bin folder with a structure similar to;

bin/dependencies/bb-tools
-Contains bin and lib folders from bbndk installation

bin/dependencies/node
-Contains node installation; Locally installed on Windows using installer or copied via tar on Mac.