HTTP/2 Cipher Suite Support

Motivation:
The HTTP/2 specification places restrictions on the cipher suites that can be used. There is no central place to pull the ciphers that are allowed by the specification, supported by different java versions, and recommended by the community.

Modifications:
-HTTP/2 will have a security utility class to define supported ciphers
-netty-handler will be modified to support filtering the supplied list of ciphers to the supported ciphers for the current SSLEngine

Result:
-Netty provides unified support for HTTP/2 cipher lists and ciphers can be pruned by currently supported ciphers
Just wanted to bring some attention here.  The reason this note is necissary is because the HTTP/2 specification (https://tools.ietf.org/html/draft-ietf-httpbis-http2-14#section-9.2.2) requires that TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 is supported.  However this cipher is only supported in java 8.  So the filter operation will never introduce incompatible ciphers, but it may possibly removed required ciphers.  The comment can be clarified if this is not clear.