Handle exceptions nicely

[ITachiLab]

There are a couple of places in the code where the default std::exception is thrown. A good programming practice is to define and use custom exceptions instead. When this is done, it would be very nice to catch those exceptions eventually, and handle them in a proper way. For the time being, any exception simply kills the app without an explanation, that is not cool.

Also look for other places where throwing a meaningful message would improve user experience (make seeing errors an amazing experience for the user).

I guess the only place where it's reasonable to catch and service the exceptions is around the DispatchMessage invocation.