Fixes #260: Visibility settings for variant member
Fixes spec on #260
Updates changelog #260
Merge pull request #262 from akeneo/fix/#260

Fix/#260
Fix issue on attribute code check
Remove mistake on attribute code
Required attributes create conflicts with configurables
Fix price attribute
Fixes price sending for configurable
Fix issue with grouped products
Merge pull request #265 from akeneo/fix_grouped_product

Fix issue with grouped products
Avoid breaking program flow if one item is invalid
Create unqiue url_key instead of relying on Magento
Magento has some problems when it comes to urk_key in the SOAP API,
as it doesn't deal with duplicate url_key
Fixes images types problem for Configurables products
Info about troubleshooting the category not found error
Visibility for Grouped products from variant
Not considered as simple products, so visible
Generate url_key for category
Add message to the log in case of error