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

git-svn-id: https://svn.apache.org/repos/asf/nutch/trunk@1619934 13f79535-47bb-0310-9956-ffa450edef68
NUTCH-1693 TextMD5Signature computed on textual content

git-svn-id: https://svn.apache.org/repos/asf/nutch/trunk@1619942 13f79535-47bb-0310-9956-ffa450edef68
NUTCH-1775 IndexingFilter: document origin of passed CrawlDatum

git-svn-id: https://svn.apache.org/repos/asf/nutch/trunk@1619944 13f79535-47bb-0310-9956-ffa450edef68