Add support for compact display options

Problem/Motivation

The spacious layout looks great, but can sometimes push menu items down below the fold, for example the Views list, or if there are a lot of content types, or taxonomies.

We could offer the users an option of making the Admin Toolbar menu more compact, to allow showing more menu items? Inspired by Claro Compact.

Steps to reproduce

• Not able to see all items, for example Views, but have to reduce browser font size.
• Find that you have to move the mouse far to get to menu items.

Default display, 6 out of 12 Views are shown.

Compact display, all 12 Views are shown.

Proposed resolution

Allow the user to make Admin Toolbar menu items more compact.

• Default
• Compact (75%)
• Medium compact (60%)
• Very compact (50%)

Remaining tasks

User interface changes

API changes

Data model changes