Eliminate references to trolltech-logo and excessive copies of qt-logo

The qt5 repositories contain four files called trolltech-logo.png – two of these really are the Trolltech logo (which we can no longer use at all), while the other two are different sized versions of the Qt logo. Additionally, the repositories contain 19 files matching "qt-logo.*", some of them being exact duplicates.

Presumably, at least three of the four trolltech-logo images should be removed (perhaps one of the ones showing a qt-logo may need to be renamed and retained), and the references to these files should be updated. Additionally, the number of copies of the qt-logo should be reduced (else imagine what will happen when marketing next decides to change the Qt logo).

A recursive grep reveals the following references to "trolltech-logo":

qlalr/doc/qlalr.qdocconf: trolltech-logo
qlalr/doc/qlalr.qdocconf: "<td align=\"right\" valign=\"top\" width=\"230\"><a href=\"http://qt.nokia.com\"><img src=\"images/trolltech-logo.png\" align=\"right\" width=\"203\" height=\"32\" border=\"0\" /></a></td></tr></table>"
qtdoc/demos/qtdemo/qtdemo.qrc: <file>images/trolltech-logo.png</file>
qtdoc/demos/qtdemo/mainwindow.cpp: this->companyLogo = new ImageItem(QImage(":/images/trolltech-logo.png"), 1000, 1000, this->scene, mainSceneRoot, true, 0.5f);
qtdoc/tools/qdoc3/doc/qdoc-manual.qdoc: "<img src=\"images/trolltech-logo.png\" \
qttools/src/doxygen/config/header.html:<td align="right" valign="top" width="230"><a href="http://qt.nokia.com"><img src="images/trolltech-logo.png" align="right" width="203" height="32" border="0" /></a></td></tr></table>
qttools/src/assistant/tools/assistant/assistant_images.qrc: <file>images/trolltech-logo.png</file>