Further improve design of left controls

[Eric-Arellano]

Follow up to #199.

• Uses touch target 44 x 44px, not 40 x 40px. On my iPhone, 40 x 40px is still fairly small. Now, we follow the web accessibility standard.
• Increases the size of the layers touch targets to 44px height. To make the touch targets look distinct and not have weird space in the middle, I added a 1px border, which mirrors the zoom-in and out buttons.
• Uses our colors for all the borders. I still don't love the color, but it can be changed later. This at least switches to our own color
• Consistently use font-size-md and non-bold text
• Vertically aligns radio buttons with label text
• Renames "Light" layer to "High contrast" for better clarity

Ideas for additional improvement:

• prettier radio button
• choose a better border color

before (before #199)

before (with #199)

after