improvements for mobile

[tyrasd]

• [ ] larger icons for better touch experience
• [ ] fix map glitches!? (Android 4.1 stock browser)
• [ ] experiment with different layouts… (map on top? switchable map & code editor?)
• [ ] …

see also: http://wiki.openstreetmap.org/wiki/Talk:Overpass_turbo#Smartphone_optimize_css

[matkoniecz]

also, consider making possible to hide query.

Screenshots from Xiaomi Redmi 4