Add a warning for unsaved work from the transcription task

[eatyourgreens]

• refactor TranscribedLinesConnector to use the withStores helper.
• add the current annotation to TranscribedLines as a prop.
• update the active annotation when we create a new transcription line from an existing line.

This PR adds annotation.update() to previously transcribed lines, which enables them to use the work-in-progress flag introduced in #2411 and #2415. It will also set them up to refresh auth tokens on update (#2563), which will allow volunteers to stay logged in when working on long pages.

Try it out on a test subject with many previously transcribed lines. If you edit a few lines, then reload the page, you should be warned that your work will be lost.

https://localhost:8080/?project=11300&subject=55414217&env=production&demo=true

Package:
lib-classifier

Closes #2564.

Review Checklist

General

• Are the tests passing locally and on Travis?
• Is the documentation up to date?

Components

• Has a storybook story been created or updated?
• Is the component accessible?
  • Can it be used with a screen reader? BBC guide to testing with VoiceOver
  • Can it be used from the keyboard? WebAIM guide to keyboard testing
  • Is it passing accessibility checks in the storybook?

Apps

• Does it work in all major browsers: Firefox, Chrome, Edge, Safari?
• Does it work on mobile?
• Can you yarn panic && yarn bootstrap or docker-compose up --build and app works as expected?

Publishing

• Is the changelog updated?
• Are the dependencies updated for apps and libraries that are using the newly published library?

Post-merging

• Did the app deploy to https://frontend.preview.zooniverse.org/projects/:project-name/:owner or https://frontend.preview.zooniverse.org/about?
• Is the new feature working or bug now fixed?
  • Is there a Talk or blog post written to announce the new feature(s)?
• Is the design working across browsers (Firefox, Chrome, Edge, Safari) and mobile?
  • Is this approved by our designer?
• Is this ready for production deployment?

[eatyourgreens]

There's overlap here with #2558. I've kept those changes in a separate commit, to minimise conflicts.

[mcbouslog]

Code changes LGTM. Tested and confirmed with transcribed lines in progress prompted if sure want to leave page (on multiple frames, with/without new lines).