Move IDeviceFactory closer to IDevice implementation

Except for the DesktopDevice, which is kind of special. Also try
a bit to make (and partially fail at doing so) naming and code
structure (#include, use of namespaces) more similar to each other.

Change-Id: I9fe266e706b72c14f59ff03ca1ae02dba3adcc71
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/android/android.pro

@@ -23,7 +23,6 @@ HEADERS += \
     androidcreatekeystorecertificate.h \
     javaparser.h \
     androidplugin.h \
-    androiddevicefactory.h \
     androiddevice.h \
     androidgdbserverkitinformation.h \
     androidqmltoolingsupport.h \
@@ -70,7 +69,6 @@ SOURCES += \
     androidcreatekeystorecertificate.cpp \
     javaparser.cpp \
     androidplugin.cpp \
-    androiddevicefactory.cpp \
     androiddevice.cpp \
     androidgdbserverkitinformation.cpp \
     androidqmltoolingsupport.cpp \