Renamed ExtensionMethods class to InternalExtensionMethods
Removed _EnumClasses.cs code file
Removed _EnumClasses.cs code file (really...)
Changed action/event firing logic and query parametrization in FakturoidInvoicesProxy
Moved enums from class to namespace.
Updated apps to use new syntax of FakturoidInvoiceProxy methods.
Fixed invalid action in SendMessage
Added more functions to demo app
Added further parameter validation