Merge branches 'cleanup/const', 'build-implicit-link' and 'build-jsonc' into integrate

Conflicts:
	cpp/Makefile
WIP on DNS.
Start of test harness.
Return leaf hash.
Temporarily include Eran's https://codereview.appspot.com/66940043/.
Also verify an inclusion proof for a leaf's hash.
Test work in progress.
Get rid of trailing whitespace.
Add missing file, move unmoved file.
Allow binary SCTs and logs on protocols other than HTTPS.
Remaining issues after a rebase.
Fix a couple of stray "https:"s.
Log responses.
Correct path.
Show error content.
Identify the type of the cert in the file name.
Calculate the right audit path length.
Get rid of cruft.