use embedded URLs for hyperlinks in the README

This switches all hyperlinks to embedded links, from a much more fragile
indirect & anonymous approach (which happens to be completely broken
on Github).

Change-Id: I92700068c7d65b50c76ce6931bff3ebab4844a49
Closes-Bug: 1335968
Redact tokens in request headers

Tokens shouldn't be logged since a token could be gathered from a
log file and used. The client was logging the X-Auth-Token and
X-Subject-Token request headers. With this change, the X-Auth-Token
and X-Subject-Token are shown as "TOKEN_REDACTED".

Also, the "Authentication" header is also redacted.

This is for security hardening.

SecurityImpact

Closes-Bug: #1004114
Closes-Bug: #1327019

Change-Id: I1edc3821ed028471102cc9b95eb9f3b54c9e2778
Merge "use embedded URLs for hyperlinks in the README"
Merge "Redact tokens in request headers"