Extendable grid data container for numerical simulations

Container structure ExtendableGrid with type stable content access and lazy content creation holding data for discretization grids for finite element and finite volume methods. Used by VoronoiFVM and GradientRobustMultiPhysics, a package for novel, gradient robust finite element methods.

Additional funtionality:

• Tools to create tensor product grids
• Tools for grid modification

Companion packages:

• Visualization of these grids and of functions on them is avaialable in GridVisualize.jl.
• The differently licensed SimplexGridFactory contains an interface which allows to create ExtendableGrid objects with Triangulate.jl which wraps the Triangle mesh generator by J. Shewchuk and TetGen.jl which wraps the TetGen mesh generator by H. Si.