Remove QTestFileLogger class.

Remove QTestFileLogger class.

This class is not very useful -- it just creates a text file that
records each occasion that an autotest enters a test function as a
stop-gap solution for the fact that the newer XML logger produces no
output if the autotest fails to terminate gracefully.  Addressing
QTBUG-20615 will provide a better solution by allowing the user to get a
partial plain text test log in those circumstances.

Change-Id: I179bb98dbd696d0734cd3f12046e5c567def30cc
Reviewed-on: http://codereview.qt.nokia.com/3390
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Rohan McGovern <rohan.mcgovern@nokia.com>