Support nested applications as extensions

[nechaido]

We need an ability to have an impress application template as a dependency.

It should allow us to write plugins locally so that it would be loaded into template server located in node_modules.

[tshemsedinov]

application/config/application.js

({
  extends: [
    'repoName', // find in `node_modules/repoName`
    'repoName/application', // find in `node_modules/repoName/application`
    '../repo/application', // relative path
    '/home/marcus/projects/repoName/application', // absolute path
  ],
});