Make QZXingFilter "official" by moving it out of the example folder

The filter is much more performant than using the QZXing API in an
imparative way for the use-case of live-analyzing video frames in QML.

examples/QZXingLive/QZXingLive.pro

@@ -4,8 +4,7 @@ QT += qml quick widgets multimedia
 
 CONFIG += c++11
 
-SOURCES += main.cpp \
+SOURCES += main.cpp
-    QZXingFilter.cpp
 
 RESOURCES += qml.qrc
 
@@ -16,6 +15,3 @@ include(../../src/QZXing.pri)
 
 # Default rules for deployment.
 include(deployment.pri)
-
-HEADERS += \
-    QZXingFilter.h

src/QZXing.pri

@@ -14,6 +14,7 @@ HEADERS += $$PWD/QZXing_global.h \
     $$PWD/CameraImageWrapper.h \
     $$PWD/imagehandler.h \
     $$PWD/QZXing.h \
+    $$PWD/QZXingFilter.h \
     $$PWD/zxing/zxing/ZXing.h \
     $$PWD/zxing/zxing/IllegalStateException.h \
     $$PWD/zxing/zxing/InvertedLuminanceSource.h \
@@ -139,6 +140,7 @@ HEADERS += $$PWD/QZXing_global.h \
 SOURCES += $$PWD/CameraImageWrapper.cpp \
     $$PWD/QZXingImageProvider.cpp\
     $$PWD/qzxing.cpp \
+    $$PWD/QZXingFilter.cpp \
     $$PWD/imagehandler.cpp \
     $$PWD/zxing/zxing/ResultIO.cpp \
     $$PWD/zxing/zxing/InvertedLuminanceSource.cpp \