Separate annotations from guard class
Documentation
Move BudgetTool and main interfaces up one level

Want to make these more prominent since they are the
gateway to the other functionality
Moving core types out of _Ext

These are programming 'helpers' and not domain specific so
I want them in the main global namespace, but I don't want
them so front and center that they detract away from the
main purpose

I use
_Core -> Missing primitives or helpers
_Ext  -> Extension methods on BCL types
Adjust namespaces on moved types