This tutorial shows how to work with vector layers and clicking

- initialize framework with 2 maps
- switch between ol3 and cesium
- activate and deactivate building and terrain layers activate
  deactivate
- open up the console to see the click events being fired when clicking on map or buildings
- normal clicking selects a single element (building or vector element), CTRL clicking adds/removes a building from or to the selection set
- invert click behavior for cesium map
- create a new vector layer, the style of the vector layer can be set or the default style is used
- the so called "selectionset" (CTRL-click) can only contain one or more buildings and is used as input for widgets such as Export
- the so called "currentItem" (click) can consist buildings and vector elements (only one at a time) and is used as input for the featureInfo widget and the CityGMLExplorer
- the style of selected objects (selectionset and currentItem) is defined in the selectBehavior "widget", see ./config.js
- add default points (height is not set so they lay on the ellipsoid)
  add styled points
- add lines (height is not set so they lay on the ellipsoid)
- add polygons (height is not set so they lay on the ellipsoid)
  add high polygons
  add vertical polygons
- activate / deactivate click listener
- clear selection set
- this doesnt work yet, does not update style of cesium objects.. dynamically change style of vector layer