Remove node_modules from starting .gitignore

We added our own version of the Compound site's .gitignore to remove
node_modules from the list.

We leave the ignores for the cached front-end CSS and JS in the
project's main .gitignore because we need to cover both directories.
Move public files to NGinx-served directory

The app/public directory is now symlinked to public, the one where files
will be served directly by NGinx.