QML Debugger refactoring

Now, QmlEngine creates the connection to the inferior (debuggee), and
notifies QmlInspector when a connection is established. Before,
inspector created the debugger engin, which was wrong.

QmlEngine's responsibilities are connecting to the debuggee and basic
QML/JS debugging features like locals & watchers, breakpoints etc.
QmlInspector takes care of Live Preview and other fancy inspection
features.

Reviewed-by: hjk

src/plugins/debugger/qml/qml.pri

@@ -1,4 +1,12 @@
+include($$PWD/../../../libs/qmljsdebugclient/qmljsdebugclient-lib.pri)
 
-HEADERS += $$PWD/qmlengine.h
-SOURCES += $$PWD/qmlengine.cpp
+HEADERS += \
+    $$PWD/qmlengine.h \
+    $$PWD/qmladapter.h \
+    $$PWD/qmldebuggerclient.h \
+    $$PWD/qmljsprivateapi.h
 
+SOURCES += \
+    $$PWD/qmlengine.cpp \
+    $$PWD/qmladapter.cpp \
+    $$PWD/qmldebuggerclient.cpp