Added basic support for custom charts

Added basic support for custom charts by automatically loading
JavaScript files from ~/Documents/Topsoil\ Scripts at startup.
Implemented basic settings system with scoping
Extended settings capabilities

Extended settings capabilities by adding several different possibilities
for batch transactions. This has resulted in significant performance
gains for the sample scatterplot.
Added settings to error ellipse chart

Added settings to error ellipse chart, refactored scatterplot, and added
transaction syntax for JavaScript.
Added script reload

Added a button under the "File" menu that reloads scripts in the
~/Topsoil\ Scripts folder.