Adding example simulations using regular and unstrucutred meshes

[shimwell]

This example will add a simple simulation with an unstructured mesh and a structured mesh to the repo

[shimwell]

While making this example I noticed we need some more functionality

Noticed that we need a

Assembly.names
Assembly.remove
Assembly.elongation.triangularity/major/minor radius

So I've made another PR to add those utils
#362