Basic revisit notation framework
Simplified revisit writing. Uses revisit profile attached to CrawlURI.
Ensure CrawlURI discards RevisitProfile after it has finished, in case
the same CrawlURI is issued again.
IdenticalDigestDecideRule now consults the new revisit profile mechanism
on the CrawlURI to determine if it represents an identical digest
revisit.
Corrected javadoc
Profiles refactored, shared elements in AbstractProfile.
WARC-Refers-To-Date now set as long and correctly formated in
getWarcHeaders.
Revisit profile is now populated with original URI and date.
Store refersToDate in String format (as intended to write in WARC).
Retain long setter for convenience.
Revisit headers now come correctly formated from the revisit profile.
ContentDigestHistoryLoader now sets the revisit profile on the CrawlURI
after determining that it is a revisit.
Merge remote-tracking branch 'internetarchive/master' into revisit-redux
Merge branch 'master' into revisit-redux

Conflicts:
	modules/src/main/java/org/archive/modules/CrawlURI.java
	modules/src/main/java/org/archive/modules/writer/WARCWriterProcessor.java
use RevisitProfile for tallying stats
set revisit profile on 304 not modified
remove deprecated unused stuff
test 304 not modified revist profile in FetchHTTPTest
oops, fix 304 tests
restore writeRevisitFor* settings, but issue warning in setter and ignore the value
Merge pull request #79 from nlevitt/revisit-redux

Revisit redux