style: replace tables with boostrap cols + css improvements

[tassiluca]

This PR includes the following style adjustment proposals:

• use bootstrap col layout + boostrap flex instead of tables for columns layout

Before

After

[giovaz94]

Excellent!

[Luca1313]

Deal on the style change, isn't the voting button missing? If so, how is rendered within it?

[tassiluca]

@Luca1313

Deal on the style change, isn't the voting button missing? If so, how is rendered within it?

The button is missing because, I don't know why, but they are not correctly categorized in "open", "closed" and "soon". Maybe a regression. I just modified the style.
Anyway, the buttons are aligned horizontally side by side (unless in mobile versions there is not enough space and they are aligned one under the other)

[giovaz94]

The approval is relative to the style change, I didn't see any error on code side.