Added enclosure based plotting

[RelativeForce]

Issues

closes #50

Summary of changes

• Added parse function that parses the String inputted into the bounds text boxes into a Rational
• Added Delta type to represent an x and y movement in Rational number space that is used for panning the bounds
• Altered the XYBounds to use Rational instead of Number
• Refactored all actions in Main that redraw the plots into a common function
• When the plots are drawn the "Rough" plot based on Number is drawn first. Once this is drawn an action is triggered to draw the "Robust" plot which is based on Approx. There is an artificial 2 seconds delay before the robust plot is drawn.
• Added RobustPlot as a data constructor of PlotCommand
• Refactored Plot.GridLines, Plot.Pan and Plot.Zoom to work with Rational bounds
• Added Plot.RobustPlot which determines a plot based on Approx where the x domain is broken into 50 segments
• Updated Components.Canvas to use new Delta type

Tests

N/A