Move schema violation docs into Schema chapter

Author: yurikhan

doc/Doxyfile.in

@@ -776,7 +776,6 @@ INPUT                  = readme.md \
                          doc/dom.md \
                          doc/sax.md \
                          doc/schema.md \
-                         doc/schema-errors.md \
                          doc/performance.md \
                          doc/internals.md \
                          doc/faq.md