First post-processing functions

[TatjanaWeiler]

Some functions to post-process LaMEM models. Plotting functions are in progress.

[boriskaus]

thanks a lot for your PR, this seems very helpful.
The only thing I wondering is whether this is not something that should rather be part of the LaMEM.jl package as it is quite specific to that code. I realise that we do have a few additional LaMEM-specific routines in here, but perhaps we should move them over as well at some stage.

If the future plotting routines you want to add will be specific to LaMEM they should go there; if they will be more general and can deal with any CartData structure, they can be added here (note that GLMakie is already an optiona; dependency of GMG).

[albert-de-montserrat]

thanks a lot for your PR, this seems very helpful. The only thing I wondering is whether this is not something that should rather be part of the LaMEM.jl package as it is quite specific to that code. I realise that we do have a few additional LaMEM-specific routines in here, but perhaps we should move them over as well at some stage.

Or alternatively, there could be a LaMEM extension in GMG, and move there also the other LaMEM-specific functions.

[mthielma]

I agree that it would be good to put all the LaMEM related functions in an LaMEM extension as Albert suggested. This way we could potentially have different extensions for different geodynamic (or other) codes. If we do this, we should however first have a plan on how the extension should look like. From summer/autumn on, I should hopefully also have hired someone who could work on this.

[boriskaus]

I'm not sure how this will work, as GMG is a fixed dependency of LaMEM.jl so I guess we would run into a circular dependency here, not?

[TatjanaWeiler]

Most of the plotting functions will work for general CartData structures.

[boriskaus]

ok, in that case let's leave the routines here