Added meter, creating key signature on demand

src/CMakeLists.txt

src/libs/core/music/tclef.h

src/libs/core/music/tmeter.cpp

src/libs/core/music/tmeter.h

src/libs/core/tnootkaqml.cpp

src/libs/core/tnootkaqml.h

src/nootka.qrc

src/qml/MainWindow.qml

src/qml/score/KeySignature.qml

src/qml/score/Meter.qml

src/qml/score/Score.qml

src/qml/score/Staff.qml