NUTCH-1409 remove deprecated properties db.{default,max}.fetch.interval, generate.max.per.host.by.ip

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NUTCH-1693 TextMD5Signature computed on textual content

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NUTCH-1828 bin/crawl : incorrect handling of nutch errors

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NUTCH-1829 Generator : unable to distinguish real errors (Mathieu Bouchard via jnioche)

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