[FLINK-6733] Remove commented out AvgAggregationFunction.java

This closes #4630.

flink-java/src/main/java/org/apache/flink/api/java/aggregation/AvgAggregationFunction.java

-package org.apache.flink.api.java.aggregation;
-/**
- * Licensed to the Apache Software Foundation (ASF) under one
- * or more contributor license agreements.  See the NOTICE file
- * distributed with this work for additional information
- * regarding copyright ownership.  The ASF licenses this file
- * to you under the Apache License, Version 2.0 (the
- * "License"); you may not use this file except in compliance
- * with the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-//package org.apache.flink.api.java.aggregation;
-//
-//
-//public abstract class AvgAggregationFunction<T> extends AggregationFunction<T> {
-//	private static final long serialVersionUID = 1L;
-//
-//
-//	@Override
-//	public String toString() {
-//		return "AVG";
-//	}
-//
-//	// --------------------------------------------------------------------------------------------
-//
-//	public static final class ByteAvgAgg extends AvgAggregationFunction<Byte> {
-//		private static final long serialVersionUID = 1L;
-//
-//		private long sum;
-//		private long count;
-//
-//		@Override
-//		public void initializeAggregate() {
-//			sum = 0;
-//			count = 0;
-//		}
-//
-//		@Override
-//		public void aggregate(Byte value) {
-//			sum += value.byteValue();
-//			count++;
-//		}
-//
-//		@Override
-//		public Byte getAggregate() {
-//			return (byte) (sum / count);
-//		}
-//	}
-//
-//	public static final class ShortAvgAgg extends AvgAggregationFunction<Short> {
-//		private static final long serialVersionUID = 1L;
-//
-//		private long sum;
-//		private long count;
-//
-//		@Override
-//		public void initializeAggregate() {
-//			sum = 0;
-//			count = 0;
-//		}
-//
-//		@Override
-//		public void aggregate(Short value) {
-//			sum += value.shortValue();
-//			count++;
-//		}
-//
-//		@Override
-//		public Short getAggregate() {
-//			return (short) (sum / count);
-//		}
-//	}
-//
-//	public static final class IntAvgAgg extends AvgAggregationFunction<Integer> {
-//		private static final long serialVersionUID = 1L;
-//
-//		private long sum;
-//		private long count;
-//
-//		@Override
-//		public void initializeAggregate() {
-//			sum = 0;
-//			count = 0;
-//		}
-//
-//		@Override
-//		public void aggregate(Integer value) {
-//			sum += value.intValue();
-//			count++;
-//		}
-//
-//		@Override
-//		public Integer getAggregate() {
-//			return (int) (sum / count);
-//		}
-//	}
-//
-//	public static final class LongAvgAgg extends AvgAggregationFunction<Long> {
-//		private static final long serialVersionUID = 1L;
-//
-//		private long sum;
-//		private long count;
-//
-//		@Override
-//		public void initializeAggregate() {
-//			sum = 0;
-//			count = 0;
-//		}
-//
-//		@Override
-//		public void aggregate(Long value) {
-//			sum += value.longValue();
-//			count++;
-//		}
-//
-//		@Override
-//		public Long getAggregate() {
-//			return sum / count;
-//		}
-//	}
-//
-//	public static final class FloatAvgAgg extends AvgAggregationFunction<Float> {
-//		private static final long serialVersionUID = 1L;
-//
-//		private float sum;
-//		private long count;
-//
-//		@Override
-//		public void initializeAggregate() {
-//			sum = 0.0f;
-//			count = 0;
-//		}
-//
-//		@Override
-//		public void aggregate(Float value) {
-//			sum += value.floatValue();
-//			count++;
-//		}
-//
-//		@Override
-//		public Float getAggregate() {
-//			return sum / count;
-//		}
-//	}
-//
-//	public static final class DoubleAvgAgg extends AvgAggregationFunction<Double> {
-//		private static final long serialVersionUID = 1L;
-//
-//		private double sum;
-//		private long count;
-//
-//		@Override
-//		public void initializeAggregate() {
-//			sum = 0.0;
-//			count = 0;
-//		}
-//
-//		@Override
-//		public void aggregate(Double value) {
-//			sum += value.doubleValue();
-//			count++;
-//		}
-//
-//		@Override
-//		public Double getAggregate() {
-//			return sum / count;
-//		}
-//	}
-//
-//
-//	// --------------------------------------------------------------------------------------------
-//
-//	public static final class AvgAggregationFunctionFactory implements AggregationFunctionFactory {
-//		private static final long serialVersionUID = 1L;
-//
-//		@SuppressWarnings("unchecked")
-//		@Override
-//		public <T> AggregationFunction<T> createAggregationFunction(Class<T> type) {
-//			if (type == Long.class) {
-//				return (AggregationFunction<T>) new LongAvgAgg();
-//			}
-//			else if (type == Integer.class) {
-//				return (AggregationFunction<T>) new IntAvgAgg();
-//			}
-//			else if (type == Double.class) {
-//				return (AggregationFunction<T>) new DoubleAvgAgg();
-//			}
-//			else if (type == Float.class) {
-//				return (AggregationFunction<T>) new FloatAvgAgg();
-//			}
-//			else if (type == Byte.class) {
-//				return (AggregationFunction<T>) new ByteAvgAgg();
-//			}
-//			else if (type == Short.class) {
-//				return (AggregationFunction<T>) new ShortAvgAgg();
-//			}
-//			else {
-//				throw new UnsupportedAggregationTypeException("The type " + type.getName() +
-//					" has currently not supported for built-in average aggregations.");
-//			}
-//		}
-//	}
-//}