Check for duplicate status code entries in 'errors' directive

Add support for default (wildcard) error page

Now logging the request body

Also don't bother showing stdout output in same situation

Need to add the name to namesObtaining each time we use the ACME client.

If another ACME client is trying to solve a challenge for a name not
being served by Caddy on the same machine where Caddy is running, the
HTTP challenge will be consumed by Caddy rather than allowing the owner
to use the Caddyfile to proxy the challenge.

With this change, we only consume requests for HTTP challenges for
hostnames that we recognize. Before doing the challenge, we add the
name to a set, and when seeing if we should proxy the challenge, we
first check the path of course to see if it is an HTTP challenge;
if it is, we then check that set to see if the hostname is in the
set. Only if it is, do we consume it.

Otherwise, the request is treated like any other, allowing the owner
to configure a proxy for such requests to another ACME client.

Logging the request body if the Content-Type is application/json or
application/xml

* dist/init/linux-sysvinit: use kill -0 to test process status

* dist/init/linux-sysvinit: use service (as root) instead of /etc/init.d/

fix typo

* Rounding the latency in certain scenarios

* run gofmt

* Fix for stripping of 'Content-Disposition' and other headers from 'X-Accel-Redirect' redirect scripts.

* Added test case for header manipulation of redirect response.

* Add default "Restricted" realm to HTTP Basic auth

* Add tests for the Basic auth realm

* Allow just one TLS Protocol

* Fix typo

Proxy: Single WebSocket connection

Proxy: Add keepalive directive to proxy to set MaxIdleConnsPerHost on transport

proxy: add Host header checking

dist/init/linux-sysvinit: execute setcap directly

`$(which setcap)` might evaluate to nothing,
and this way the error thrown will be more clear.
If setcap is not available on Debian/Ubuntu,
you can install the package `libcap2-bin`