Added Raw, an std::ostream manipulator to print possibly non-terminated buffers

Added Raw, an std::ostream manipulator to print possibly non-terminated buffers
and their labels/sizes.

The Raw manipulator tries to be smart about printing buffers at various
debugging levels: Large buffers are only printed at DBG_DATA by default.
This allows the caller to mix higher-level debug messages with dumping
of potentially large volumes of data. This smartness can be overruled
using an explicit minLevel() method call.