player/qt: move player api wrapper into a qml extension library

A further step is moving the qmlglsink element into an extension so there is no need for writing any c++ code!

playback/player/qt/extension/extension.pro

+TEMPLATE = lib
+CONFIG += qt plugin
+QT += qml quick
+CONFIG += c++11
+DEFINES += GST_USE_UNSTABLE_API
+TARGET = qmlplayerextension
+
+# Additional import path used to resolve QML modules in Qt Creator's code model
+# QML_IMPORT_PATH =
+
+HEADERS += qplayerextension.h \
+    qgstplayer.h \
+    player.h \
+    quickrenderer.h \
+    imagesample.h
+
+SOURCES += qplayerextension.cpp \
+    qgstplayer.cpp \
+    player.cpp \
+    quickrenderer.cpp \
+    imagesample.cpp
+
+unix:!macx {
+QT_CONFIG -= no-pkg-config
+CONFIG += link_pkgconfig
+PKGCONFIG = \
+    gstreamer-1.0 \
+    gstreamer-player-1.0 \
+    gstreamer-tag-1.0
+}
+
+macx {
+    QMAKE_MAC_SDK = macosx10.9
+    INCLUDEPATH += /Library/Frameworks/GStreamer.framework/Headers
+
+    LIBS += \
+        -framework AppKit \
+        -F/Library/Frameworks -framework GStreamer
+}