Examples: Clean the pro files

Remove useless set of MOC_DIR, OBJECT_DIR,
RCC_DIR and UI_DIR.

Change-Id: Iba08d517e096a982f2bae9701083ebc40ee78ea2
Reviewed-by: Jens Bache-Wiig <jens.bache-wiig@digia.com>
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>