CRM-9290 UI uses JS to do what can be done with CSS

This is small, but irritating...
In the following places, the UI is using javascript for no good reason:

• Highlighting a contact and showing links in the "recently viewed" block onHover
• Highlighting a row in a table onHover
• Hovering over a crm-accordion-header
• Hovering a menu item in the admin menu
• Probably other hover properties, it seems fairly ubiquitous

In these situations, the css :hover property would be a much better choice.
The reason I even noticed this is because the JS itself is buggy, and often doesn't "let go" when the mouse stops hovering over the given element.