Add custom user settings UI.

- Adds UI in the keyboard help menu for setting custom GUI settings remembered
through localStorage.
- Adds option for force container support regardless of provider.
- Adds option to set the environmentName regardless of the deployment.
- Adds option to disable the EU cookie notice.
Is there a reason this needs to be an inline style? Would really be a lot better if it were in the CSS. These would probably live in `stylesheet.less` inside `#shortcut-help {...}`.