Add manage usage route to user menu

[srartese]

Checklist

1. If you've added code that should be tested, add tests
2. If you've changed APIs, update (or create!) the documentation
3. Ensure the tests pass
4. Make sure that your code lints and that you've followed [our coding style]
   (https://github.com/kobotoolbox/kpi/blob/master/CONTRIBUTING.md)
5. Write a description of your work suitable for publishing on our forum
6. Mention any related issues in this repository (as #ISSUE) and in other repositories (as kobotoolbox/other#ISSUE)
7. Open an issue in the docs if there are UI/UX changes

Description

This adds a link to the user menu to route to '#/accounts/usage' in order for users to view their account submission, storage, transcription minutes, and translation minutes usage.

[srartese]

I did not format code as to not mess up git history but looking into how to get a change made to beta in this branch so we don't have to worry about it