Move occ.pri in src/occtools

Also "install" rule creates a "qmake/" folder with files "compiler_config.pri" and "occ.pri" inside
Remove 3rdparty/
qttools_core: add qt_plugin_def.h
Add qmake/modules.pri, making easy inclusion of FougTools in the build procedure
Remove messages in modules.pri
Make qtviewer example compile with Qt4