Add Qt5 support

• Fix compilation when PythonQt is not used.
• Fix CMakeLists.txt regarding PythonQt.
• Update PythonQt decorators.
• Import PythonQt at startup
• Remove unused OSGWidget::wid and add decorator to get window ID
• Do not add mainWindow and osg variable to Python
• Add MainWindow class decorator to PythonQt.
• Homogenize calls to WindowsManager
• Use scoped_lock to avoid deadlock on exception.
• Remove URDF caching based on file timestamp.
• Minor change
• Fix ColorMap
• Add bug between Qt and OSG in README.md
• [CMake] Handle compatiblity with mac
• Add QCustomPlot example.
• Use Qt 4 by default.
• Make plugin for QCustomPlot disabled by default.
• Add plugin pyqcustomplot (GPL License)
• Clean MatplotlibWidget
• Hack to fix SEGV when calling IDL createWindow from embeded python interpreter.
• Add error message if trying to load python plugin without PythonQt
• Handle dock widget containing OSGWidget properly (visibility of central widget)
• Add OSGWidget::wid to get access to the window ID from Python.
• Make MainWindow::createView accessible to Python
• Show gepetto logo when no dock widget is visible.
• Add missing #ifdef in settings.cc
• Update PyQgv bindings and move it to QGraphViz package.
• Add ability to load python scripts instead of python module.
• Expose more functions in PyQgv
• Fix compilation warning.
• Fix parsing of arguments
• OSGWidget are created as dock widget.
• Remove references to hpp-gui when possible.
• Fix CMake
• [CMake] Fix extra flag in pkg-config
• Use Qt mechanism to check Qt version.
• Fix compilation for Qt >= 5.5.1
• Fix compilation of PyQgv plugin.
• Force single threaded OSG widget when with Qt5
• Compatibility of plugins with Qt5
• Write qtversion to pkg config file.
• Properly handle Qt styles
• Make CMake compliant with Qt5
• Minor changes to prepare switch to Qt5
• Fix FindPythonQt.cmake
• Update documentation
• Improve QGV bindings
• Add pyqgv plugin.
• Add skeleton for C++ plugin
• Follow change in PythonQt