Simplify logging

Let VerboseWriter solely handle logging to the destination file.
qt_message_handler takes the role of logging to cout. This allows
us to get rid of the twisted stream logic in utils.cpp, and
furthermore let us get rid of the buggy debugstream.

Change-Id: I5cf2e41b126a90025825a0d93f95b41d783ef22a
Task-number: QTIFW-524
Reviewed-by: Karsten Heimrich <karsten.heimrich@digia.com>
Reviewed-by: Niels Weber <niels.weber@digia.com>
Simplify VerboseWriter

This class does not need to be a QObject.

Also, rename 'setOutputStream' to more accurate 'setFileName'.

Change-Id: Iefb5997bb1ee1d5c54fa9abbdd3ad81f5d9a49d8
Reviewed-by: Karsten Heimrich <karsten.heimrich@digia.com>