Update resource extraction script and service worker to work with Webapp files new location

[latin-panda]

Because of the migration, the original js/inbox.js and templates/inbox.html have new location.

There are some places that will need update:

• resource extraction script
• service worker
• grunt tasks (possibly, will check)
• unit test

[latin-panda]

There were some additional changes during this work, reposting the PR's description:

• Updated location references for: main.js and styles.css
• Moved and renamed from src/templates/inbox.html to src/ts/index.html to match angular guidelines. The output location (/index.html) is the same as before this PR.
• Updated name references for: index.html (webapp entry point)
• Added task to clean extracted-resources before extracting, this is done in start-up only.
• Moved extracted-resources one level up so it's out of the /api/src directory. New location: /api/extracted-resources
• Fixed e2e of service worker
• Added unit test coverage for new task in resources.