Include javadoc/source in Java release packages.

Also fixed javadoc errors.

[ci skip]
diff --git a/java/pom.xml b/java/pom.xml
index 2d7161b..2d8e9a1 100644
--- a/java/pom.xml
+++ b/java/pom.xml
@@ -152,6 +152,32 @@
       <build>
         <plugins>
           <plugin>
+            <groupId>org.apache.maven.plugins</groupId>
+            <artifactId>maven-source-plugin</artifactId>
+            <version>2.2.1</version>
+            <executions>
+              <execution>
+                <id>attach-sources</id>
+                <goals>
+                  <goal>jar-no-fork</goal>
+                </goals>
+              </execution>
+            </executions>
+          </plugin>
+          <plugin>
+            <groupId>org.apache.maven.plugins</groupId>
+            <artifactId>maven-javadoc-plugin</artifactId>
+            <version>2.9.1</version>
+            <executions>
+              <execution>
+                <id>attach-javadocs</id>
+                <goals>
+                  <goal>jar</goal>
+                </goals>
+              </execution>
+            </executions>
+          </plugin>
+          <plugin>
             <artifactId>maven-gpg-plugin</artifactId>
             <version>1.6</version>
             <executions>