Fixes #8380: Adds a grunt based development server for livereload and prototyping.

This adds a grunt based development server that Bastion or a plugin
can start and have all the assets automatically loaded. This means that
all routes provided by the plugin or Bastion can be accessed on port
9000 and all api/data calls will be proxied to your running Rails
server.
RFE: would like to be able to set this dynamically or in a config file (my rails server is running on a different host vm)