Write plain text to the common Cantera logger to be more consistent with the
verbose/debug logging from other parts of Cantera. This simplifies several of
the transport initialization functions, and eliminates the need for class
XML_Writer.
These changes make it unnecessary to copy header files around during
the build process, which tends to confuse IDEs and debuggers. The
headers which comprise Cantera's external C++ interface are now in
the 'include' directory.
All of the samples and demos are now in the 'samples' subdirectory.
