Fix Qt plugin packaging in Windows.

A CMake error meant that they went to individual sub directories
rather than one single directories per type.

Code/Mantid/Build/CMake/WindowsNSIS.cmake

@@ -124,10 +124,10 @@ install ( FILES ${CMAKE_CURRENT_SOURCE_DIR}/Installers/WinInstaller/qt.conf DEST
 # imageformats
 set ( QT_PLUGINS_IMAGEFORMAT qgif4.dll qico4.dll qjpeg4.dll qmng4.dll qsvg4.dll qtga4.dll qtiff4.dll )
 foreach( DLL ${QT_PLUGINS_IMAGEFORMAT} )
-  install ( FILES ${CMAKE_LIBRARY_PATH}/qt_plugins/imageformats/${DLL} DESTINATION plugins/qtplugins/imageformats/${DLL} )
+  install ( FILES ${CMAKE_LIBRARY_PATH}/qt_plugins/imageformats/${DLL} DESTINATION plugins/qt/imageformats )
 endforeach()
 # sqlite
-install ( FILES ${CMAKE_LIBRARY_PATH}/qt_plugins/sqldrivers/qsqlite4.dll DESTINATION plugins/qtplugins/sqldrivers/qsqlite4.dll )
+install ( FILES ${CMAKE_LIBRARY_PATH}/qt_plugins/sqldrivers/qsqlite4.dll DESTINATION plugins/qt/sqldrivers )
 
 ###########################################################################
 # Include files/libraries required for User compilation

Code/Mantid/Installers/WinInstaller/qt.conf

 [Paths]
-plugins = ../plugins/qtplugins
\ No newline at end of file
+plugins = ../plugins/qt