[#982] [#977] [#858] Allow to transfer the content a ChannelHandlers inbound/outbound buffer on removal/replacement

This changes the behavior of the ChannelPipeline.remove(..) and ChannelPipeline.replace(..) methods in that way
that after invocation it is not possible anymore to access any data in the inbound or outbound buffer. This is
because it empty it now to prevent side-effects. If a user want to preserve the content and forward it to the
next handler in the pipeline it is adviced to use one of the new methods which where introduced.

 - ChannelPipeline.removeAndForward(..)
 - ChannelPipeline.replaceAndForward(..)