fixed warnings in dialog module when PURE_QML_ONLY is defined

There are a couple of unused parameters in that case.

Change-Id: Ica81621e7d74474cbfa0b54c20501ecc72661c08
Reviewed-by: Liang Qi <liang.qi@digia.com>
Add currentColor property to ColorDialog.

QColorDialog has this property. This patch effectively means that
the color property will be set when the dialog closes, instead of
whenever the current color in the dialog changes, so pressing cancel
will revert the color to what it was before the dialog was opened.

[ChangeLog][QtDeclarative][ColorDialog] Added currentColor property.

Change-Id: I2ef6b32954342cd2469cf1552d53f9e2fbf3420b
Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com>