Add loading of system functions

Searches the class (including the partial class) for anything with a
macroattribute on it. Eventually this macroattribute will be able to
tell it whether it's lazyparsing arguments or not, as well as perhaps
other important information.
Created first command - Date

Date has 2 overloads, one that takes a format string, and another that
defaults to yyyy-MM-dd. Both return today's date in the selected format.