md-fab: High Contrast mode has no focus indicator

[hansl]

At all.

[jelbourn]

@crisbeto since you're on Windows, could you do a pass on the components in high-contrast mode and add styles to make things better?

[crisbeto]

Here's what I got:

• Fab buttons are barely visible when focused and impossible in high contrast mode.
• Really hard to see whether raised buttons (accent, primary, warn) are focused.
• Button toggles don't have any hover indication.
• Checkboxes don't have focus indication.
• Radio buttons don't have focus indication.

I'll try to take care of most of them, although the slider and tooltip will need a little bit more work.