Switch to new config format

Configuring only with environment variables is not sustainable in the long run. With these changes, here's how config will work:

Configuration
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* All application configuration is done in `config/modulusui.conf.js`. 
* When you run `grunt build`, Grunt will compile this config file into a format suitable for AngularJS and will store that compiled file at `app/config.js`.
* Within AngularJS, inject `Config` anywhere in the app to get access to the configuration as a JS object.

Environment Variable Overrides
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Set a `MODULUS_UI_CONF` environment variable, containing JSON of config variables. The variables in `MODULUS_UI_CONF` will override any in `modulusui.conf.js` during the Grunt build process.


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This PR also stops using the global config variables from the App, with a switch to the `Config` object, and removes `index.html.template` since it's no longer necessary.