Move Default Printing Speed out of the "Other" Catagory

[d_barnette]

I would like to be able to control the print speed per layer in the same way that the Temperature and Cooling are controlled. It would be nice to be able to control the print speed at various z heights when printing multiple items sequentially, as the speed could be varied as desired within a single process per item.

Besides, why should an item as important as Printing Speed be relegated to the "Other" category? It should have it's own tab, just like the Temperature and Cooling have, IMO.

Darrel