Restore the ability to specify the location of Node and NPM.

Default is still to search the system path.  Build properties: `nodePath` and `npmPath`.
Merge pull request #1893 from AnalyticalGraphicsInc/configureNodePath

Restore the ability to specify the location of Node and NPM.
Merge remote-tracking branch 'origin/master' into renameDynamicScene-vertexPositions