Improve error handling

[Moneyl]

Error handling needs to be improved. Right now there's several places where functions can return a .Err result and leave it unhandled, crashing the app. There's also no way for it to log additional info to the application using it.

• Add logging event so RfgTools can log errors and information and apps that use it can add an event handler to pass them through their own logging system.
• Go through code and make sure all functions that return a Result<> type are handling the error case. Change the functions to return Result<> themselves if necessary. Could use the Try!() mixin to simplify the code in that case.