Restructure apps

[pixelblend]

This restructuring has several benefits:

• Allows third-party libraries to be safely installed and mounted
• Allows shared libraries for an app to be available between internal and external apps

The new structure is set out as follows:

- apps/app_name
   - src
       - internal.html  <-- /app_name on internal port
       - external.html  <-- /app_name on external port
       - lib
         - my_lib.js    <- /app_name/lib/my_lib.js on both ports
   - node_modules       <- /app_name/modules on both ports
   - assets             <- /app_name/assets on both ports

Related PRs:

• https://github.com/bbc/enloudinator-radio/pull/5
• https://github.com/bbc/peeps_and_cake/pull/9

[andrewn]

Shall we update update to install dependencies in another PR?

[pixelblend]

Added dependency installation in https://github.com/andrewn/neue-radio/pull/58