maxzoom is not honoured while editing a visualization

[strk]

Visualizations have a "max zoom" parameter which is used by the embed_map but not the map editing ui.

This results in async behavior between what you see and what you get (#217).

\cc @javisantana

[saleiva]

#218

[strk]

As of 2.5.0 the maxzoom associated with a base map is honoured. I cannot zoom more than allowed by the basemap, and if I change basemap to one with a lower maxzoom a zoom-out happens.
Good job, whoever did it ! [ I don't know which commit fixed this ]