Refactored configuration for javascript examples.
Deactivated broken JS examples.
Better error message when no Javascript emitter is specified.
Add more notes about how to install node.
Add an extra argument for enabling nodejs support.

This is essentially using the v8 emitter plus setting a #define.
Simplification in common javascript example Makefile.
Added examples to Javascript module documentation.
Add note about '-node' command line flag for Node.js code generation.