Add catches to all promises

[hukka]

It seems that in some cases promises don't have a .catch() attached on any level. This means that any throws will get silently ignored. For example https://github.com/City-of-Helsinki/kerrokantasi-ui/blob/master/src/actions/user.js#L9 can fail with HTTP level error, or the JSON simply isn't what it should be, or https://github.com/City-of-Helsinki/kerrokantasi-ui/blob/master/src/components/BaseCommentForm.js#L80 might read a malformed base64 (this wasn't an exhaustive list).

[akx]

Probably not all promises, but those where it makes sense.

Also, care should be taken to figure out what should be done in those catch handlers.

[hukka]

Well, I wonder if it's easier to judge everything case by case and whenever the relevant code is modified compared, than having logging handlers for everything. Sure, it is a bit of code bloat, but coding errors could happen anywhere.

[akx]

Maybe we oughta just slap on an unhandledrejection handler then?

window.addEventListener("unhandledrejection", function(err, promise) { 
  
});