Default Dirichlet Behavior

[alistairbntl]

It seems that in some cases, when the Dirichlet boundary flags are not set properly, the Dirichlet boundary conditions can be set across the entire domain rather than just on the boundary. When this happens, the solution is simply an interpolation of the boundary condition functions. The default behavior should probably warn the user that the boundary flags have not been set properly. I will update this issue once I have a simulation which replicates the error.

[adimako]

@alistairbntl any progress with this? Still an issue? @tridelat any view on this?