Update sample from CQ 5.6 to 5.6.1

Between 5.6 and 5.6.1 some changes were made to better handle error conditions. These changes prevent the sample from working on 5.6.1. This pull request resolves [issue 1](https://github.com/paolomoz/cq-commerce-impl-sample/issues/1) and comes via Levente Santha who kindly helped me with the fix.

Some files committed in error (e.g. target files) are also tidied up in this changeset.