conneg inputs are now stateless and fed by InputNode.  Also Closes GH-638
minor refactoring on OutputBehavior's media selection
added ILogger to IFubuRequestContext
input and output behavior use the logger from IFubuRequestContext
made outputbehavior use the stateless writers.  Also closes GH-641, Closes GH-646
killing a duplicated method on InputNode
eliminated the attachment policies in favor of a lighter method on BehaviorChain
using limited interfaces for BehaviorChain.Input/Output.  Closes GH-637
BehaviorChain.Authorization uses an interface.  Closes GH-648