Added many plots support and bounds input

[RelativeForce]

Issue(s)

closes #31
closes #18

Changes

• Added Color type to represent a colour. A colour can be a HexCode string, RGBA record or a named colour like "Red". NamedColor was added as a type-safe way to refer to specific colours instead of using strings.
• Formatted Components.Canvas.Draw
• ExpressionPlot to hold all the plotted data of an expression plot. This resides in the main state whereas each ExpressionInput maintains its own temporary state.
• The Main component now has a button labelled "Add plot" which will add another ExpressionInput slot.
• Formatted Types module
• Added bounds input component
• Updated README.md to describe how to run the app locally
• Renamed the server script in npm with start so the developer can just type npm start

Unit test changes

N/A