kcms/nightlight: Drop icon theme hack, switch map zooming icons to the new lightweight +/- symbols
Even with the new magnifier icons the buttons looked infinitely worse than any other alternative. That's not to say the icons are bad, they are just not suitable for zooming maps imho. So we introduced simple zoom-plus & zoom-minus icons like every other GIS software out there.
They are links to list-add and list-remove because we want them to look like a simple + and - signs, which appears to be a widespread convention in most GIS software. We don't want maps to have zoom icons with a magnifying glass because a magnifying glass is already used for search buttons/fields which are also fairly common in such apps.
While at it, switch to symbolic versions.
Comparison:
| Status Quo | Magnifier |
|---|---|
 |
 |
Other software:
| Name | Screenshot |
|---|---|
| Google Maps |
 
|
| OsmAnd+ |  |
| 2GIS |  |
| Yandex |  |
| Apple Maps |  |
I don't see a single magnifying glass icon smh. Except for "search".