Remove expect and unwrap from codebase

[chvck]

If we're going to fail something we should do it gracefully and at least attempt to give the user some information about why we've failed. We shouldn't just panic.

[chvck]

expect and unwrap in main.rs are probably ok, these happen at startup. unwrap when taking a lock also ok, this can only happen if the lock has been poisoned, i.e. a panic occurred in another thread which has holding the lock - this a) shouldn't be happening and b) is probably unrecoverable.

[Westwooo]

@chvck What about the numerous engine_state.ctrlc.as_ref().unwrap().clone(); ? Also there are a few places where we do serde_json::to_string(json).unwrap() and we know we are passing in valid json since it's a server response. And I'd say that Runtime::new().unwrap(); seems okay.