[Feature] Ability to skip product url rewrite processing

[fazed]

Hi,

This PR adds the ability to skip URL rewrite processing when saving products.

My current use-case is having issues when updating product information when no category information is passed to the product data object. This causes the url rewrite processor to throw exceptions, in my case it throws a duplicate primary key constraint.

There might be a deeper issue here, namely its trying to insert already existing entries into the catalog_url_rewrite_product_category table. This is probably caused by the lack of information given in the passed product data object and its url rewrite diff fails causing existing rewrites to be returned - and inserted. I have not tested this theory since adding a skip configuration option circumvents this issue altogether.