Small fixes

[jjeffryes]

This PR addresses a variety of small visual issues.

• the beta label has a tooltip if the user is not in testnet mode.
• the superfluous info icon next to the coupon label in purchase was removed
• a placeholder was added for the coupon input in purchase
• the coupon input being blank is now handled separately from an invalid code
• the ... button on the user page was removed
• the windows controls were updated to look more like Mac controls and be centered properly
• other nav bar icons that were off center vertically were fixed

Closes #789, 790, 791, 788, and 786

[rmisio]

The middle icon gets an underline when you hover over it. I'm assuming it shouldn't since the others don't and it arguably looks cleaner without.

[morebrownies]

Noticed the same issue that @rmisio reported above too. Otherwise, looks good to me.

[jjeffryes]

Huh. Good catch. I'm not sure how that happened. Will investigate and update later tonight.

[jjeffryes]

@rmisio underline removed.