3D: update cesiumjs to version >= 1.57

[danduk82]

as : a map.geo.admin.ch user i want : the 3D viewer of map.geo.admin.ch to use the latest version of cesium, at least v=1.57 (2019-05-01) because: it implements a lot of performance improvements, such as fast loading tiles

MUST have:

• cesium version >= 1.57
• works on official BIT Edge v.42 browser (see below and this issue)
• feature parity with current version of map.geo.admin.ch (production)
• integration in map.geo.admin.ch using advantage of fast loading tiles implementation
• does not compromise the functioning of any non 3d-related features of map.geo.admin.ch

NB:

• if the BIT Edge v.42 browser should not support the latest version of cesium, a selector must be implemented to activate an older version of cesium when Edge browser v.42 is detected. The chosen fallback version of cesium should be the most recent that is supported by Edge v.42.

[pakb]

That will be ugly, but we could target specific version of Edge comparing window.navigator.userAgent with a bunch of userAgents from this website. As I said, ugly, but that should work (we should default to latest Cesium version though)