Customize Netty ServerBootstrap (fixes #494)

This pull request adds customization hooks for `ChannelHandler` and channel options to NettyJaxrsServer in resteasy-netty and resteasy-netty4.

It enables users to customize Netty's `ServerBootstrap` in a limited way which can be used to add [logging](http://netty.io/4.0/api/io/netty/handler/logging/LoggingHandler.html), [transparent compression](http://netty.io/4.0/api/io/netty/handler/codec/compression/ZlibDecoder.html) handling, and [other things](http://netty.io/4.0/api/io/netty/channel/class-use/ChannelHandler.html).

This fixes #494.