QmlApp: Only use QMLJSDEBUGGER define to activate qml debugging

Don't confuse users by two defines they have to comment in when
they just want to 'debug': Instead QMLJSDEBUGGER now activates
both the Js Debugger & and the QmlObserver services. Finetuning
can still be done by using the (undocumented) NO_JSDEBUGGER,
NO_QMLOBSERVER defines.

share/qtcreator/qml/qmljsdebugger/qmljsdebugger-lib.pri

@@ -9,14 +9,16 @@ contains(CONFIG, dll) {
 }
 
 ## Input
+!contains(DEFINES, NO_JSDEBUGGER) {
 HEADERS += \
     include/jsdebuggeragent.h \
     include/qmljsdebugger_global.h
 
 SOURCES += \
     jsdebuggeragent.cpp
+}
 
-contains(DEFINES, QMLOBSERVER) {
+!contains(DEFINES, NO_QMLOBSERVER) {
     include($$PWD/editor/editor.pri)
 
     HEADERS += \