Remove focus outlines on touch devices

Assumption: touch-based devices users are much less likely to use use a
physical keyboard (Tab) for navigation.

Also, remove redundant CSS rules for disabling the outline in other
places and use outline: 0 instead of outline: none which seems to be
correct according to specs. [1]

[1] https://developer.mozilla.org/en-US/docs/Web/CSS/outline

Change-Id: I0ac8cf9a6bce8d525e553cae449cb17ab4d6de68
Merge "Remove focus outlines on touch devices"