Until now the identification from 3D map view used tolerance based
on the current view of the main 2D map canvas - that was giving often
unexpected results if the 2D map canvas had significantly different
zoom level from the 3D map view.
Until now the tool only considered terrain. This commit adds support
for 3D renderers created from vector layers, so it is possible to
correctly identify polygons and linestrings in 3D.
