Add icons

[planktonic]

We’re missing some useful icons:

• directional arrows with arrow shafts
• circle-icons with only an outline circle
• ellipsis
• clock
• cog
• download
• upload
• external link
• show/hide (eye/eye-crossed-out?)
• document
• folder
• heart
• star
• link
• location
• map
• location
• telephone
• comment
• reply
• user

Also:

• ensure the thickness of lines match
• rename the caret- icons to chevron-