Yet another plugin rename

For consistency we should use "plugin" as suffix
on plugin names.

Change-Id: Ieea483cc1d7642e4fcd7d0907de8efd7e00743e1
Reviewed-by: Caroline Chao <caroline.chao@digia.com>
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>

src/controls/controls.pro

-TARGET  = qtquickcontrols
+TARGET  = qtquickcontrolsplugin
 TARGETPATH = QtQuick/Controls
 
 QT += qml quick gui-private core-private

src/controls/qmldir

 module QtQuick.Controls
-plugin qtquickcontrols
+plugin qtquickcontrolsplugin
 ApplicationWindow 1.0 ApplicationWindow.qml
 Button 1.0 Button.qml
 CheckBox 1.0 CheckBox.qml

src/private/private.pro

-TARGET  = qtquickcontrolsprivate
+TARGET  = qtquickcontrolsprivateplugin
 TARGETPATH = QtQuick/Controls/Private
 
 QT += qml quick gui-private core-private

src/private/qmldir

 module QtQuick.Controls.Private
-plugin qtquickcontrolsprivate
+plugin qtquickcontrolsprivateplugin
 AbstractCheckable 1.0 AbstractCheckable.qml
 Control 1.0 Control.qml
 FocusFrame 1.0 FocusFrame.qml