Add magic wand tool.

The magic wand tool selects regions that are similar in
colour to the pixel that the user touched. The threshold of
similarity is controlable by a slider in the Toolbax options
panel. A threshold of 0 means the colours must be identical, a
theshold of 100 means that all colours will be selected.
For example, using distance of two colours in RGB-space, the
distance between red and magenta is 50 out of 100.
Add selection dragging and marching ants

Selections can be dragged around. The dashed border is also
animated to appear like 'marching ants'.