Better error handling

[karoliineh]

As pointed out by @vesalvojdani in #26, the extension just crashes 5 times when the GobPie configuration is missing from the project root.

In this pull request

• The preAnalyzeCommand is made fully optional (can be missing from the configuration file)
• If GobPie conf is missing from the project root, the MagPieBridge server is still launched, but without being able to do any analyses. This way the extension does not crash. It is made so that it waits and checks until the conf file is created and then restarts the server automatically.
• Error messages are more meaningful and try to be more helpful. In particular, as the MagPieBridge server is running in any case, it is possible to send messages to the user using the popup to check for the messages in the terminal, where there are either Goblint or GobPie (more meaningful) error messages present.
• Changed the info type logs that are supposed to be error logs to the appropriate type.

[vesalvojdani]

Seems a bit roundabout to tell the user to check the log for a simple one line error message that prevents the thing from starting. Why not display it directly?