Remove qmake build files

Removes qmake as a build system for building Qt Creator itself.
Keep them for some tests that are not completely moved to CMake yet.

Change-Id: I846c6ef65626b6dfae6375fdc85d00677aa8c2fb
Reviewed-by: hjk <hjk@qt.io>
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/imageviewer/imageviewer.pro

@@ -1,30 +0,0 @@
-include(../../qtcreatorplugin.pri)
-
-HEADERS += \
-    exportdialog.h \
-    imageviewerplugin.h \
-    imageviewerfactory.h \
-    imageviewerfile.h \
-    imageviewer.h \
-    imageview.h \
-    imageviewerconstants.h \
-    multiexportdialog.h
-
-SOURCES += \
-    exportdialog.cpp \
-    imageviewerplugin.cpp \
-    imageviewerfactory.cpp \
-    imageviewerfile.cpp \
-    imageviewer.cpp \
-    imageview.cpp \
-    multiexportdialog.cpp
-
-!isEmpty(QT.svg.name) {
-    QT += svg
-    greaterThan(QT_MAJOR_VERSION, 5) : QT += svgwidgets
-} else {
-    DEFINES += QT_NO_SVG
-}
-
-FORMS += \
-    imageviewertoolbar.ui

src/plugins/imageviewer/imageviewer_dependencies.pri

@@ -1,6 +0,0 @@
-QTC_PLUGIN_NAME = ImageViewer
-QTC_LIB_DEPENDS += \
-    extensionsystem \
-    utils
-QTC_PLUGIN_DEPENDS += \
-    coreplugin