Similarly to raster calculator, mesh calculator can take dataset groups from current mesh layer and
combine them with various aritmentic/logical operators to new dataset group.
Introducting MDAL, QgsMeshLayer, mesh data providers (mesh_memory, mdal)
to read and visualize raw meshes: vertices and faces. Support dragging
2dm files from browser on canvas to visualize 2dm meshes.
Support for QgsMeshLayer in Python API.