[#1293] Fix IllegalBufferAccessException in HttpPostRequestDecoder

* Also let HttpPostRequestDecoder extends Iterator and let its Exceptiosn extend DecoderException
[#1340] Log SslExceptions thrown by SslEngine.closeInbound() with debug level
[#1340] use full url in comment
[#1344] Fix race condition in DefaultChannelPromise / DefaultChannelProgressivePromise which could lead to listeners that are not notified
[#1346] Make sure HttpPostRequestEncoder.nextChunk() return LastHttpContent once all chunks are read
Same fix for Netty V4 for issue #1313

Remove encodeAttribute/decodeAttribute for Multipart element
Replace where necessary by cleanString (to remove '"') on name part (not
on value part)
Correctly handle multipart disposition
Allow to recover from exception triggered by accept() more easily

This is done by stop accept() new sockets for 1 seconds
Beside this this commit also makes sure accept() exceptions of OioServerSocketChannel trigger
the fireExceptionCaught(...). The same is true fo the AioServerSocketChannel.
[maven-release-plugin] prepare release netty-4.0.0.CR2
[maven-release-plugin] prepare for next development iteration