Front-end Error Handling: by default show error message from server when showing error

Guideline:

• Use the standard izi toast function method that is created (this.showErrorMessage) and hook into it.
• If an error is defined in the axios error, display it.
• Else, display a default error. (based on HTTP status code if possible).

Add proper frontend error messages when something wrong happens https://gitlab.ewi.tudelft.nl/TI2806/2017-2018/ED/ed3/ed3/issues/301