Move CSFML source files to CSFML/ directory

This helps make it easier to distinguish SFML files from CSFML files.
This is especially important for CSFML private headers which are
often C++ code with .hpp file extensions. This change means SFML and
CSFML can use headers with the same name without conflict.

doc/doxyfile.in

@@ -966,7 +966,7 @@ WARN_LOGFILE           =
 # spaces. See also FILE_PATTERNS and EXTENSION_MAPPING
 # Note: If this tag is empty the current directory is searched.
 
-INPUT                  = "@DOXYGEN_INPUT_DIR@/include/SFML" \
+INPUT                  = "@DOXYGEN_INPUT_DIR@/include/CSFML" \
                          "@DOXYGEN_INPUT_DIR@/doc/mainpage.hpp"
 
 # This tag can be used to specify the character encoding of the source files