Fix priority of LoggerPreprocessor

[imagejan]

Logger parameters should be processed before InitPreprocessor, so that plugins can use a Logger in their initializer.

Closes #446.

[ctrueden]

@imagejan Thanks! So the change to VERY_HIGH ends up moving the LoggerPreprocessor to before the InitPreprocessor (which is HIGH) but still after the ServicePreprocessor (which is 2*VERY_HIGH). That's intended, right?

[imagejan]

Thanks for merging, @ctrueden!
Exactly, moving LoggerPreprocessor priority in between ServicePreprocessor and InitPreprocessor was intended.