Make exceptions reporting consistent and containing useful information

Currently failures and errors are reported in many inconsistent ways over the message queue. For example the message describing a problem can be reported in one of "payload.exception.err", "payload.reason.kwargs.reason", "payload.exception.message", "payload.exception", while the status code for web requests can be found in one of "payload.reason.kwargs.code", "payload.status", "payload.exception.status_code", "payload.exception.kwargs.code". On the other hand a lot of information is missing in case of exceptions - for example stacktraces.

There are many situations where proper exception reporting would be useful - for example collection of them into an interface like Sentry (https://getsentry.com/welcome/). Due to many possible ways of serialising stacktraces, I propose using raven/sentry format (https://sentry.readthedocs.org/en/latest/developer/interfaces/index.html#sentry.interfaces.Stacktrace). Other tools should be easy to adapt if needed.