Test property placeholder with multiple locations and default values.

Issue: SPR-10619

 - cherry-pick of pull request #257, which originally applied to 3.2.x

Issue: SPR-10394

# By Chris Beams (1) and Dave Syer (1)
* SPR-10579:
  Polish pull request #291 per committer guidelines
  Make CommandLinePropertySource enumerable

 - Update Apache license headers
 - Remove trailing whitespace
 - Edit original commit comment to use 'Issue:' syntax
 - Revert use of diamond operator (<>) in main sources

See committer guidelines at
https://github.com/SpringSource/spring-framework/blob/master/CONTRIBUTING.md

Issue: SPR-10579

JOpt 4.4 has enumerable options, so this change can be made
if we upgrade. The only awkward thing is that JOpt allows
aliases for options, so we have to pick one to avoid double
counting. This implementation picks the last one in the list
which is the alphebtically last of the long options, if there
are any (e.g. "o1", "option1" returns "option1"). Most of the
time there will only be one or two aliases for each option so
it won't matter.

Issue: SPR-10579

The submitted pull requests for SPR-10572 did not build.

This commit fixes the MergePlugin to create from configurations rather
than the project. It also removes unnecessarily added code that was
commented out.

Issue: SPR-10572

Recently Spring framework build has been updated to use Gradle 1.6.
With the new version some of the Gradle APIs have been deprecated.
These deprecated APIs have been used by Spring build specific Gradle
plugins, which resulted in deprecation warnings in build output.

This patch changes Spring build specific Gradle plugins to use new
Gradle APIs instead of deprecated ones.

Even after this change build still produces warnings about Gradle
deprecated APIs being used. These come from Spring shared Gradle
plugins and other 3rd party Gradle plugins in use, like Gradle
Artifactory Plugin (GAP), which are still not updated to Gradle 1.6.
Related tickets for updating of these plugins to Gradle 1.6 are
GRADLE-53 and GAP-144, and once they get resolved Spring framework
build should further be updated.

Issue: SPR-10572

Update README adding explicit JDK instructions

Re-order subsections to make it clear that running a full
`./gradlew build` is not necessary just to import projects
into your IDE or to build and install jars to your .m2 cache.

Add a test to ensure that the CI server does not accidentally build
with the wrong JDK version.

Issue: SPR-10569

Issue: SPR-10514

Issue: SPR-10449

Issue: SPR-10547

Issue: SPR-10436

This change involves a modification of the "writeContent" template method to include the "jsonPrefix" String instead of the "prefixJson" boolean flag. Since said template method has only been introduced in 3.2.2, this change should hopefully not be a problem.

Issue: SPR-10567

Issue: SPR-10568

Issue: SPR-10374

Issue: SPR-10546
(cherry picked from commit 6e4317eb)

Previously ConfigurationClassParser could override a nested
@Configuration without consideration of @Bean's defined in parent
classes.

This commit ensures that if the original ConfigurationClass contains
additional bean definitions it is processed again.

Issue: SPR-10546
(cherry picked from commit 940011e2)

Issue: SPR-10398

Commit 5b1165 was an attempt to leave semicolon content in the URL path
while ignoring it for request mapping purposes. However, it becomes
quite difficult to manage and semicolon content should not always be
ignored (sometimes a semicolon is used as a separator of multiple items
in a path segment, rather than for matrix variables).

This change effectively reverts back to the original approach in 3.2
where a flag on AbstractHandlerMapping can be used to have semicolon
content removed or kept. If kept, path segments with matrix variables
must be represented with a path segment.

The main difference is that by default it is removed everywhere
including the MVC namespace and Java config.

Issue: SPR-10427, SPR-10234

Previously DeferredResult locked around the setting of the result
including handling up to the part of submitting a dispatch. This
can cause a deadlock if a timeout occurs at the same time since
the Tomcat timeout thread has its own locking that permits only
one thread to do timeout or dispatch processing.

The fix reduces the locking to cover only the attempt to set the
DeferredResult but not the dispatching.

Issue: SPR-10485

Issue: SPR-10556