Fixes #130 Add method to obtain product quantity in cart regardless of attributes

<a href='#crh-start'></a><a href='#crh-data-%7B%22processed%22%3A%20%5B%22https%3A//github.com/zencart/zc-v1-series/pull/131%23issuecomment-52797837%22%2C%20%22https%3A//github.com/zencart/zc-v1-series/pull/131%23issuecomment-52810523%22%2C%20%22https%3A//github.com/zencart/zc-v1-series/pull/131%23issuecomment-52810747%22%5D%2C%20%22comments%22%3A%20%7B%22General%20Comment%22%3A%20%7B%22html_url%22%3A%20%22https%3A//github.com/zencart/zc-v1-series/pull/131%23issuecomment-52797837%22%2C%20%22comments%22%3A%20%5B%7B%22body%22%3A%20%22If%20I%20didn%27t%20know%20the%20reasons%20why%20those%20commented%20lines%20were%20left%20in%20there%2C%20I%27d%20say%20take%20them%20out.%20%5Cr%5Cn%5Cr%5CnOtherwise%2C%20follows%20pattern%2C%20and%20previous%20suggestions%20have%20been%20incorporated%20satisfactorily.%5Cr%5Cn%3A%2B1%3A%20%22%2C%20%22created_at%22%3A%20%222014-08-20T15%3A48%3A11Z%22%2C%20%22user%22%3A%20%7B%22avatar_url%22%3A%20%22https%3A//avatars.githubusercontent.com/u/404472%3Fv%3D2%22%2C%20%22html_url%22%3A%20%22https%3A//github.com/drbyte%22%7D%7D%2C%20%7B%22body%22%3A%20%22%3A%2B1%3A%20%22%2C%20%22created_at%22%3A%20%222014-08-20T17%3A18%3A01Z%22%2C%20%22user%22%3A%20%7B%22avatar_url%22%3A%20%22https%3A//avatars.githubusercontent.com/u/227354%3Fv%3D2%22%2C%20%22html_url%22%3A%20%22https%3A//github.com/zcwilt%22%7D%7D%2C%20%7B%22body%22%3A%20%22%3Ashipit%3A%22%2C%20%22created_at%22%3A%20%222014-08-20T17%3A19%3A46Z%22%2C%20%22user%22%3A%20%7B%22avatar_url%22%3A%20%22https%3A//avatars.githubusercontent.com/u/227354%3Fv%3D2%22%2C%20%22html_url%22%3A%20%22https%3A//github.com/zcwilt%22%7D%7D%5D%2C%20%22title%22%3A%20%22General%20Comment%22%7D%7D%2C%20%22approved%22%3A%20%7B%22https%3A//github.com/zcwilt%22%3A%20%7B%22avatar_url%22%3A%20%22https%3A//avatars.githubusercontent.com/u/227354%3Fv%3D2%22%7D%7D%7D'></a>
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- [x] <a href='#crh-comment-General Comment'></a> <img src='http://www.codereviewhub.com/site/github-completed.png' height=16 width=60>&nbsp;<b><a href='https://github.com/zencart/zc-v1-series/pull/131#issuecomment-52797837'>General Comment</a></b>
- <a href='https://github.com/drbyte'><img border=0 src='https://avatars.githubusercontent.com/u/404472?v=2' height=16 width=16'></a> If I didn't know the reasons why those commented lines were left in there, I'd say take them out.
Otherwise, follows pattern, and previous suggestions have been incorporated satisfactorily.
:+1:


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