Add supporting MQTT 3.1.1

Motivation:

MQTT 3.1.1 became an OASIS Standard at 13 Nov 2014.
http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/mqtt-v3.1.1.html
MQTT 3.1.1 is a minor update of 3.1. But, previous codec-mqtt supported only MQTT 3.1.

Modifications:

- Add protocol name `MQTT` with previous `MQIsdp` for `CONNECT`’s variable header.
- Update client identifier validation for 3.1 with 3.1.1.
- Add `FAILURE (0x80)` for `SUBACK`’s new error code.
- Add a test for encode/decode `CONNECT` of 3.1.1.

Result:

MqttEncoder/MqttDecoder can encode/decode frames of 3.1 or 3.1.1.
SPDY: add support for pushed resources in SpdyHttpDecoder

Motivation:

The SPDY/3.1 spec does not adequate describe how to push resources
from the server. This was solidified in the HTTP/2 drafts by dividing
the push into two frames, a PushPromise containing the request,
followed by a Headers frame containing the response.

Modifications:

This commit modifies the SpdyHttpDecoder to support pushed resources
that are divided into multiple frames. The decoder will accept a
pushed SpdySynStreamFrame containing the request headers, followed by
a SpdyHeadersFrame containing the response headers.

Result:

The SpdyHttpDecoder will create an HttpRequest object followed by an
HttpResponse object when receiving pushed resources.
Add more test cases to ZlibTest

Motivation:

Currently, we only test our ZlibEncoders against our ZlibDecoders. It is
convenient to write such tests, but it does not necessarily guarantee
their correctness. For example, both encoder and decoder might be faulty
even if the tests pass.

Modifications:

Add another test that makes sure that our GZIP encoder generates the
GZIP trailer, using the fact that GZIPInputStream raises an EOFException
when GZIP trailer is missing.

Result:

More coverage for GZIP compression
Revert bad renaming in ZlibTest
Small performance improvements

Motivation:

Found performance issues via FindBugs and PMD.

Modifications:

- Removed unnecessary boxing/unboxing operations in DefaultTextHeaders.convertToInt(CharSequence) and DefaultTextHeaders.convertToLong(CharSequence). A boxed primitive is created from a string, just to extract the unboxed primitive value.
- Added a static modifier for DefaultHttp2Connection.ParentChangedEvent class. This class is an inner class, but does not use its embedded reference to the object which created it. This reference makes the instances of the class larger, and may keep the reference to the creator object alive longer than necessary.
- Added a static compiled Pattern to avoid compile it each time it is used when we need to replace some part of authority.
- Improved using of StringBuilders.

Result:

Performance improvements.
Adding codeAsText to HttpResponseStatus.

Motivation:

I found myself writing AsciiString constants in my code for
response statuses and thought that perhaps it might be nice to have
them defined by Netty instead.

Modifications:

Adding codeAsText to HttpResponseStatus that returns the status code as
AsciiText.

In addition, added the 421 Misdirected Request response code from
https://tools.ietf.org/html/draft-ietf-httpbis-http2-15#section-9.1.2

This response header was renamed in draft 15:
https://tools.ietf.org/html/draft-ietf-httpbis-http2-15#appendix-A.1
But the code itself was not changed, and I thought using the latest would
be better.

Result:

It is now possible to specify a status like this:
new DefaultHttp2Headers().status(HttpResponseStatus.OK.codeAsText());
Clean up 000d3a55c5b771b7ed8b71f54b44de72a85306c0

- Rename httpResponseStatus() to newStatus()
  - Move newStatus up so that static methods are grouped together
- Rename codeAsString to codeAsText
Use Proxy-Authorization instead of Authorization for proxy authentication

Motivation:

When authenticating with a proxy server, HttpProxyHandler should use the
'Proxy-Authorization' header rather than the 'Authorization' header.

Modifications:

- Use 'Proxy-Authorization' header

Result:

Can connect to an HTTP proxy server
Add logLevel property to enable different log levels for the examples.

Motivation:

When running the examples using the provided run-examples.sh script the
log level is 'info' level. It can be handy to be able to configure a
different level, for example 'debug', while learning and trying out the
the examples.

Modifications:

Added a dependency to logback-classic to the examples pom.xml, and also
added a logback configuration file. The log level can be configured by
setting the 'logLevel' system property, and if that property is not set
the default will be 'info' level.
The run-examples.sh was updated to show an example of using the system
property to set the log level to 'debug'

Result:

It is now possible to turn on debug logging by settnig a system property
on the command line.
Add HttpStatusClass

Related: #3157

Motivation:

It should be convenient to have an easy way to classify an
HttpResponseStatus based on the first digit of the HTTP status code, as
defined in the RFC 2616:

- Information 1xx
- Success 2xx
- Redirection 3xx
- Client Error 4xx
- Server Error 5xx

Modification:

- Add HttpStatusClass
- Add HttpResponseStatus.codeClass() that returns the class of the HTTP
  status code

Result:

It's easier to determine the class of an HTTP status
Backport the IntObjectHashMap changes in f23f3b9617b01095416334060ca8379316946e5c

Motivation:

The mentioned commit contains a bug fix and an improvement in
IntObjectHashMap that requires backporting.

Modifications:

Update IntObjectMap, IntObjectHashMap, and IntObjectHashMapTest

Result:

Easier to backport HTTP/2 and other changes in master in the future
Do not write LastHttpContent twice in HttpStaticFileServer example

Related: #3122

Motivation:

The HttpStaticFileServer example writes the LastHttpContent twice at the
end of the transfer.  HttpChunkedInput already produces a
LastHttpContent at the end of the stream, so there's no reason to write
another.

Modifications:

Do not write LastHttpContent in HttpStaticFileServerHandler when
HttpChunkedInput is used to transfer a file.

Result:

HttpStaticFileServer does not violates the protocol anymore.