webapp refactory with grunt + require.js + backbone

adds a duplicate of the `webapp` directory (called `webapp_bb`) in `protocoder/protocoder_app/src/main/assets` to work on the webapp refactory. also adds `node_modules` in `.gitignore`.

HOW TO USE:
from command line: 
1) cd to the `webapp_bb` directory
2) `npm install` to install the dependencies (requires Node.js installed)
3) `grunt` to run the watcher: whenever a .js, .html or .less file is modified, grunt will run the compiler in the background for you.