This commit provides a detailed overview of the current block download
method, which I've retroactively named blocks-first for parallelism with
headers-first.
New And Significantly Revised:
* New Initial Block Download (IBD) section (h3) with Blocks-First
subsection (h4)
* New Orphan Block subsection (under Blocks Broadcasting) describing
orphan blocks and how they're handled under blocks-first. Also
includes a simple illustration of the difference between orphan blocks
and stale blocks. Thanks to luke-jr for his s/orphan block/stale
block/ commit a couple months ago---that made this commit much easier.
Edits:
* Cleaned up a couple cases missed by previous s/orphan/stale/ commit
because they used past tense (orphaned).
* In P2P reference section, mentioned that a `block` message can be sent
unsolicited by miners.
* Mention that `getheaders` and `headers` were added in protocol
version 31800.
* Moved a few internal links around and added a few new internal links.
Administrivia:
* Started adding "TODOv0.10" in HTML comments to places that need to be
updated when 0.10 is released so that I can easily git grep for that
tag later.
Thanks also (in alphabetical order) to @cbeams, @mikehearn, and
@tgeller, among others.
The last pre-squash commit was: c2b8d562aa107c7b68c60946cea14cdccc5159ad
