new model to handle Product Rep Images

ref #82

bake the model for this table

have ProductRepresentativeImage belongTo Product and Product hasOne
ProductRepresentativeImage

also  addin the following code for the ProductRepImage model

public $actsAs = array(
        'Upload.Upload' => array(
            'filename' => array(
                    'thumbnailSizes' => array(
                        'xvga'  => '1024x768',
                        'vga'   => '640x480',
                        'thumb' => '80x80'
                )
            )
        )
    );

    public $virtualFields = array(
        'thumb_url' =>
'CONCAT("/files/product_representative_image/filename/",ProductRepresent
ativeImage.id,"/thumb_",ProductImage.filename)',
        'view_url' =>
'CONCAT("/files/product_representative_image/filename/",ProductRepresent
ativeImage.id,"/",ProductImage.filename)'
    );
add in the folder to store the product rep images

ref #82
ignore the other images stored in the product_representative_image folder

ref #82