Show plus/minus zoom buttons, especially when including a Leaflet raster pane

[almccon]

In cases where I'm working on trying to design a vector style to match a legacy raster style, I often get onto non-integer zooms and the raster style looks bad, and it's not a useful comparison.

It would be nice to have the old-school plus/minus buttons that I could use for zooming in and out to keep myself at integer zoom levels.