Cherry-pick of 5717e6bd68c227c03e766ef09527b

First steps to have a proper admin area with its own menu
Cherry-pick of 34832ebf3aeb199afdadf892e

Adding chosen.js
Temporary moving the workers view link to the admin menu

I know it's not the correct place, but
the current location looks even worse to me
User management view in the admin area