WaterSums - Alpha Four release (0.1.3)

This latest release comes after a wonderful holiday spent in the beautiful Grampians in western Victoria (in Australia). Most of the new functionality in this release relates to the completion of the integration of undo/redo support. All project edits can now be undone and then redone, including project and network edits, changes made in the curve editor and in pulldown menus. A few bug fixes are included.