Support Boundary Conditions and Loads

I'm currently working with a dataset where the Displacements and the loads are stored in the .inp file alongside the grid. Currently it's not possible to read them through FerriteMeshParser.

I'll try to get this to work, however, I'm not sure how to best output the resulting Boundary Conditions and Loads, as the Ferrite `Grid` struct can't carry this information.

Maybe this should just be a seperate function that can read the boundary conditions and loads? Should this function then return a FerriteMeshParser specific struct that has the boundary condition information?