Support for RestClient like ClientLogger for RestResources

[akil-rails]

The RestClient library provides a nice interface ClientLogger, with a default implementation DefaultClientLogger for rest clients.

A similar interface for RestResource with a default Implementation would be make it so much easier for implementing logging for RestResources. Currently, one has to find a way to implement this using filters, or writers, which are all far more error-prone in the user space (especially when dealing with bodies using entityStream), and such a interface would make it trivial for users to provide their own implementations.