Initial add of area_curve
Refactored steps into functions and included multiple area polygons.
Correction to rectangle (Riemann Sum) algorithm.
Included area as well as Riemann Sum rectangles.
Debugging Riemann Sum.
Debugging Riemann Sum.
Refactoring.
Code cleanup.
Included slider control.
Changed slider control colour.
Slider events.
Included another function.
Copy of trunk to area_curve_functionalised as there is plan to unfunctionalise parts of the script to allow easier event handling.