No more Job spinner

Since the mui5 migration the loading spinners don't disapear after loading. for the events this isn't a problem. As they cover the spinner after load. for the jobs it's a problem as they are transparent most of the time. I don't know how to fix this. therefore I have just removed the spinners. The job images normally load really fast, as they are small. therefore the spinner wouldn't show for very long.

@lutzsa if you have time feel free to fix them properly and add them back in. closes #72 (closed)