Add Poco::SharedLibrary example

Using Poco user guide on Poco::SharedLibrary as a guide, implement
simple main program using this to load two shared libraries in
sequence and access function symbols from them. Add simple shared
library interface as function taking and returning void.
Reinstate logging output
Add example using Poco::ClassLoader

Implement MicroPipeline "library" with pure abstract base class
"IProcessingModule" for steps in a processing pipeline. Provide it
with the required name interface method for use by Poco, plus a simple
process method taking and returning an int.

Provide example concrete implementation "MyProcessingModule" containing
two concrete class of IProcessingModule. Implement the required methods,
making the process method do simple multiplication and addition, plus
reporting to stdout of the calls. Add the Manifest generation needed by
Poco's ClassLoader interface, and build the classes into a shared
module.

Add mp_classloader application with Poco::ClassLoader and Poco::Manifest
instances for loading IProcessingModule concrete classes. Load
MyProcessingModule library, printing out Manifest contents as first
task. Then create instances of the classes supplied by
MyProcessingModule into a vector to act as a dumb pipeline. Create a
sequence of 100 integers, and pass these through the pipeline in turn.