Clear screen when zooming.

This prevents artifacts of previously displayed content to appear outside of the draw area (when the currently drawn area is smaller than the previously drawn area).
Merge pull request #6911 from BevapDin/clear-screen-on-zoom

Clear screen when zooming.
Merge branch 'master' of https://github.com/CleverRaven/Cataclysm-DDA into rename-qualities
Improve the output of item qualities.
Having the numbers on the left side leads to an aligned output.