Fix issues with new Cesium version

[forman]

Use of Cesium 0.66 introduced several new issues:

• Fix adding a point - crash, see console
• Fix adding a line - no error on console, only marker points shown, but connecting line shown, no line placemark added
• Fix adding a polygon - error on console, only marker points shown, but connecting line shown, no line placemark added
• Fix adding a rectangle - no error on console, nothing shown, no placemark added
• Fix "countries" layer almost invisible in map

EDIT

• Fix copy CSV, WKT, GeoJSON to clipboard, it no longer works, clipboard remains empty (see Fix copy-to-clipboard #41)

EDIT

• After drawing a few entities, selection by clicking works, then suddenly stops working, selection marker sticks to a random entity

[forman]

Progress so far:

• insertion of points works
• selection of entities not at all (markers sticks either to an entity or view center, randomly)
• insertion of other geometries works 2, or 3x, then drawing adn insertions are hidden like if they were inserted on another layer
• increasing z-Order did not solve the problem
• copying entities from source to target collection including removal from source collection did not solve the problem

[dzelge]

Sometimes the shape draws but disappears immediately.

[forman]

Fixed by #61