Domain name normalization

[yuliya-ivaniukovich]

At the moment strings like www.domain.com, domain.com, subdomain.domain.com are treated as individual jobs with independent results. This can lead to some data collisions since we use document URL as a key of document tabel.
We should:

• investigate if www.domain.com and domain.com are treated as the same address in Heritrix
• for subdomains we can have independent Heritrix jobs, but we should link them to already existing documents if they were downloaded and checked before within another job.