Expose toolbar to plugin (replaceable)

qgroundcontrol.qrc

src/FactSystem/FactControls/FactPanelController.cc

src/FlightDisplay/FlightDisplayView.qml

src/PlanView/PlanToolBar.qml

src/PlanView/PlanView.qml

src/QGCApplication.cc

src/QGCApplication.h

src/QGCPalette.h

src/QmlControls/QGCToolBarButton.qml

src/QmlControls/QGroundControl.Controls.qmldir

src/QtLocationPlugin/QMLControl/OfflineMap.qml

src/api/QGCCorePlugin.cc

src/api/QGCOptions.cc

src/api/QGCOptions.h

src/ui/MainRootWindow.qml

src/ui/MainWindow.ui

src/ui/MainWindowHybrid.qml

src/ui/MainWindowInner.qml

src/ui/toolbar/MainToolBar.qml