Also alter CrawledDocument to not require String parsing of the underlying byte[] data. This should reduce the number of large memory allocations quite significantly, hopefully reducing the GC churn a bit.
* Restructure the code to make a bit more sense
* Store full headers in crawl data
* Fix bug in retry-after header that assumed the timeout was in milliseconds, and then clamped it to a lower bound of 500ms, meaning this was almost always handled wrong
