Option to sort memoryMaps on save

[DanChianucci]

When the model is saved, it would be great if Kactus would (optionally?) sort the memoryMap before saving.

Currently the model is saved in an unsorted state. For example if Register A is at address 0, and register B is at address 1, the xml may still list register B first. I believe that the order is determined by the order that the elements are added in the GUI.