Separate out examples.

Pull out examples from the source files into seporate test.
Also put all the template code together into logger.h.
Also change the api: Log the object itself rather than the address.
Combine all files into log.h.

This library can now be used just by including log.h. See example2.cpp.
Update README.md to use log.h.
Remove #define PATH_SIZE from logfile.h. It is no longer needed.