Add tests for CSV and XML import conversion scripts

[stephanegigandet]

Import.pm has a lot of features to read XML or CSV files of various formats provided by manufacturers to extract the values we are interested in, and to normalize them.

We need test scripts that ensure that those conversion features do not get broken by new changes.

Proposal:

• for each of the convert_*_data.pl scripts, commit a sample input file (e.g. with 100 products) and the resulting (aka "golden") converted file.
• have the script run on the sample input, and compare the output with the golden output.