Polish Javadoc for @Sql and SqlScriptsTestExecutionListener
Document @Sql script support in the reference manual

 - Introduced a new "Executing SQL scripts" section in the Testing
   chapter with a subsection covering programmatic script execution via
   ResourceDatabasePopulator, ScriptUtils, etc. and a subsection
   dedicated to the new declarative support via @Sql.

 - Documented @Sql, @SqlConfig, and @SqlGroup in the "Annotations" and
   "Meta-annotation" sections.

 - Fixed broken cross-reference links to "false positives" with ORM tip.

 - Documented methods in JdbcTestUtils.

 - Improved layout and information in sections covering
   AbstractTransactionalJUnit4SpringContextTests and
   AbstractTransactionalTestNGSpringContextTests.

Issue: SPR-11849
Document Groovy script support in the TCF

This commit documents support for using Groovy scripts to load
ApplicationContexts using the Spring TestContext Framework (TCF) in the
reference manual.

Issue: SPR-12027
Polish Javadoc for MergedContextConfiguration
Document @TestPropertySource support in the reference manual

This commit introduces a new "Context configuration with test property
sources" section in the Testing chapter of the reference manual.

In addition, the "Context caching" section has been updated regarding
support for test property source locations and properties in
MergedContextConfiguration.

Issue: SPR-12076
Document programmatic tx mgt support in the TCF

This commit introduces a new "Programmatic transaction management"
section in the Testing chapter of the reference manual with an example
highlighting the new support provided via TestTransaction.

In addition, this commit begins the work to be addressed more
thoroughly in SPR-11399 by overhauling the entire "Transaction
management" section with in-depth discussions on the following topics.

 - Test-managed transactions
 - Enabling and disabling transactions
 - Transaction rollback and commit behavior
 - Executing code outside of a transaction
 - Configuring a transaction manager

Issue: SPR-11941, SPR-11399
Improve text for xref links in the reference manual
Document automatic discovery of default TELs

This commit introduces a new "TestExecutionListener registration and
ordering" section in the Testing chapter of the reference manual.

Issue: SPR-12082
Document support for merging TELs with defaults

This commit restructures the content of the "TestExecutionListener
registration and ordering" section of the Testing chapter in the
reference manual into cross-referenced subsections with more
appropriate titles.

In addition, this commit introduces a new "Merging
TestExecutionListeners" subsection which documents the new MergeMode
feature in @TestExecutionListeners, including an example demonstrating
the MERGE_WITH_DEFAULTS mode.

Issue: SPR-12083
Add 'new in Spring 4.1' section to reference manual

This commit introduces a new-in-4.1 section in the reference manual with
initial content for testing improvements.