[imp] Massive import

[FedericoLaTorre]

When massive import is used, with a máx processing batch, ie. 50, it never imports more than 50-100 products. Since it is a long process it should import 50 products everytime it's used. With current functionality, you need to speciffy the exact amount of products, or more, to import all the active publications, wich leads to a time out if not properly configured.