Better error handling

[LourensVeen]

Goal: no exceptions come out no matter what you put in. Except the ones produced by cwltool in the output, those are not my responsibility.

[LourensVeen]

• Recover database after a crash
• Reconnect to compute resource if connection is lost
• Inspect source and think about what could go wrong
• Make fuzz test

[LourensVeen]

This should be quite good now, although I'd still like to do the above inspection and fuzz test just because I'm a perfectionist. So I'm going to leave this open, but it should be considered mostly fixed.