fix error reporting in OutwatchTracing

handle errors properly in dynamic content (IO/Observables) (outwatch#545

)

* handle errors properly in dynamic content (IO/Observables)

- always write to the console
- render an error element with the exception into the dom

fixes outwatch#544

* make error modifier configurable and empty per default

* show errors on localhost by default

* fixed tests and added testcase for disabling error reporting

Co-authored-by: Florian Witteler <github@flwi.de>

remove publish settings from build.sbt

Update RxScala.js version

Update to RxScala.js 0.13.4

Fix selected attribute

Large scale refactor

Version bump

Update to new scalajs version