fix windows script to use correct env var (backported and updated the 0.4.0 release zip)

Author: kimchy

bin/elasticsearch.bat

@@ -21,7 +21,7 @@ set JAVA_OPTS=^
  -XX:+CMSParallelRemarkEnabled^
  -XX:+HeapDumpOnOutOfMemoryError
 
-set ES_CLASSPATH=$CLASSPATH;"%ELASTICSEARCH_HOME%/lib/*"
+set ES_CLASSPATH=$CLASSPATH;"%ES_HOME%/lib/*"
 set ES_PARAMS=-Delasticsearch -Des-foreground=yes -Des.path.home="%ES_HOME%"
 
 "%JAVA_HOME%\bin\java" %JAVA_OPTS% %ES_JAVA_OPTS% %ES_PARAMS% -cp "%ES_CLASSPATH%" "org.elasticsearch.bootstrap.Bootstrap"