Eliminate all Javadoc warnings

- Support external Javadoc links using Gradle's javadoc.options.links

 - Fix all other Javadoc warnings, such as typos, references to
   non-existent (or no longer existent) types and members, etc,
   including changes related to the Quartz 2.0 upgrade (SPR-8275) and
   adding the HTTP PATCH method (SPR-7985).

 - Suppress all output for project-level `javadoc` tasks in order to
   hide false-negative warnings about cross-module @see and @link
   references (e.g. spring-core having a @see reference to spring-web).
   Use the `--info` (-i) flag to gradle at any time to see project-level
   javadoc warnings without running the entire `api` task. e.g.
   `gradle :spring-core:javadoc -i`

 - Favor root project level `api` task for detection of legitimate
   Javadoc warnings. There are now zero Javadoc warnings across the
   entirety of spring-framework. Goal: keep it that way.

 - Remove all @link and @see references to types and members that exist
   only in Servlet <= 2.5 and Hibernate <= 4.0, favoring 3.0+ and 4.0+
   respectively. This is necessary because only one version of each of
   these dependencies can be present on the global `api` javadoc task's
   classpath. To that end, the `api` task classpath has now been
   customized to ensure that the Servlet 3 API and Hibernate Core 4 jars
   have precedence.

 - SPR-8896 replaced our dependency on aspectjrt with a dependency on
   aspectjweaver, which is fine from a POM point of view, but causes
   a spurious warning to be emitted from the ant iajc task that it
   "cannot find aspectjrt on the classpath" - even though aspectjweaver
   is perfectly sufficient. In the name of keeping the console quiet, a
   new `rt` configuration has been added, and aspectjrt added as a
   dependency to it. In turn, configurations.rt.asPath is appended to
   the iajc classpath during both compileJava and compileTestJava for
   spring-aspects.

Issue: SPR-10078, SPR-8275, SPR-7985, SPR-8896

spring-orm-hibernate4/src/main/java/org/springframework/orm/hibernate4/support/OpenSessionInViewInterceptor.java

@@ -50,17 +50,8 @@ import org.springframework.web.context.request.async.WebAsyncUtils;
  * transactions via {@link org.springframework.orm.hibernate4.HibernateTransactionManager}
  * as well as for non-transactional execution (if configured appropriately).
  *
- * <p><b>NOTE</b>: This interceptor will by default <i>not</i> flush the Hibernate
- * <code>Session</code>, with the flush mode being set to <code>FlushMode.NEVER</code>.
- * It assumes that it will be used in combination with service layer transactions
- * that handle the flushing: the active transaction manager will temporarily change
- * the flush mode to <code>FlushMode.AUTO</code> during a read-write transaction,
- * with the flush mode reset to <code>FlushMode.NEVER</code> at the end of each
- * transaction. If you intend to use this interceptor without transactions, consider
- * changing the default flush mode (through the {@link #setFlushMode "flushMode"} property).
- *
  * <p>In contrast to {@link OpenSessionInViewFilter}, this interceptor is configured
- * in a Spring application context and can thus take advantage of bean wiring..
+ * in a Spring application context and can thus take advantage of bean wiring.
  *
  * <p><b>WARNING:</b> Applying this interceptor to existing logic can cause issues
  * that have not appeared before, through the use of a single Hibernate
@@ -71,8 +62,6 @@ import org.springframework.web.context.request.async.WebAsyncUtils;
  *
  * @author Juergen Hoeller
  * @since 3.1
- * @see #setSingleSession
- * @see #setFlushMode
  * @see OpenSessionInViewFilter
  * @see org.springframework.orm.hibernate4.HibernateTransactionManager
  * @see org.springframework.transaction.support.TransactionSynchronizationManager