Mobile UI cleanup

[figureone]

A few style issues on mobile devices and small screens:

• Options tabs can be better
• User list actions
• Dashboard widget should take up full width at all screen sizes

Make elements take full width (username, role, date, ignore button, ban button, local user icon, multisite user icon) at the different wp screen sizes:

normal (width > 1800px)
min-width: 1500px, max-width: 1800px
min-width: 800px, max-width: 1499px,
max-width: 799px