[UPD] In create method, use name field unless name_get

In create method, use name unless name_get to define res_name value.
In account.voucher model, the name_get return the amount, and we don't want this, we would like to get the name field.
I think this must be more defensive. Every model is guaranteed to have a name_get, but 'name' is just a field that may or may not exist.
At least, you should check for existence of this field and fall back to name_get if necessary.
But in general, I'm not sure if it's a good idea to prefer a name field to name_get. There are a lot of reasons why a model would decide to have another name than 'name'. Wouldn't it be better to keep a list of known bad models ('account.voucher' for now) that get special treatment, and use name_get otherwise?