New function: add_fault!() in 3D

[aelligp]

adds a function add_fault!() that adds a straight fault from Start to End coordinates with a thickness of e.g. 5 and a Dip angle -10:

add_fault!(Phase, Temp, Grid;
        Start=(20,100), End=(10,80),
        Fault_thickness=5.0,
        Depth_extent=(-25.0, 0.0),
        DipAngle=-10.0,
        phase=ConstantPhase(1)
        )

Also in this PR: fix add_volcano

[albert-de-montserrat]

Thanks, cool PR!

[aelligp]

@boriskaus the workflow for the joss paper draft has been removed

Changes have been addressed