vis: Make tooltips hoverable

1. Nest "a" and "span" elements inside "div" instead of nesting "div" and "span" inside of "a" - makes the whole tooltip not a hyperlink.

2. Move tooltip closer to the mouse, so we can maintain :hover on the "div" and move over to the tooltip.

3. Don't move the tooltip thet far to the left, for short logs it used to create empty space between cell and the tooltip.

4. Use a "figure space", as a filler, instead of   - it's wider and it's necessary to have sensible width of "a" element now.

5. Cleanup CSS - remove all the styling that does not change anything.

Cc: @mupuf