There should be replaced stacktrace loggings to stderr with usage of logging.

On many places both in server and in components there is called on exception printStackTrace, this results in having the stacktrace printed to stderr. This results in each line of the stacktrace to be considered a new error message in logs.

Using stderr is
1) is inefficient from performance point of view and
2) it doesn't have such nice control of what and when should be printed (length of stacktrace,log level) as logging does.

I believe occurrences of using the printStackTrace in the code should be reviewed and either removed or replaced with logging where appropriate.

This one is reported for the server itself. If you agree that it is worth doing as I believe it is, then there should be created separate tasks for individual components.