Update threshold selector mobile layout

https://www.sketch.com/s/396d2645-b2c4-47c1-8f43-14365a0ec9f7/a/Wda4qpw#Inspect

Try to fit everything without scrolling on smaller screens.

• Show only edit icon on smaller screen
• Clip overflowing threshold color thumbnails and show +3 etc. instead
• Use textOverflow: 'ellipsis', whenever possible
• Fine tune cell width and paddings

Related issue: #680 (closed)