Add Autoscaling of potentials

- Can be toggled with boolean "autoScale" in Animation class

- Autoscale is not necessarily a desirable feature. Thus should
also add a "Preferences" control panel to allow the user to
choose how to scale potential and current values.
Add preferences Window with Animation rotation and Voltage Scaling

- Still need to add Current Scaling, circuit size?
Change polarity of a battery in circuit by clicking near its end
Add current autoScale and separate ShowCurrents toggle

- Separated "Show Values" into "Show Voltages" and "Show Currents".
These operate independently.

- Added to the Preferences window to include Autoscale and Manual
Scaling options.

- Found bug in Circuit class. It does not reliably find short
circuits in more complex circuits (e.g. a window shape with
three resistors, one battery and 7 wires.) As a result, the
animation behaves strangely.
Modify package