Fixing multiselect equls

[mamazu]

Fixes #163

[TalkMarc]

Thank you for looking into this.
Sadly this doesn't fix this issue:
$value->getCustomerOptionType() is functionally equivalent to the $curItemCustomerConfiguration[$code]->getOptionValue() logic in that foreach, so there is still an "Call to a member function getCustomerOptionType() on array" error.

[mamazu]

Thanks for testing. Of course you're right. I've updated the code again. I think this should be correct now, but I found it pretty hard to add tests, if you have any idea for that.