Prior to this commit, the `getAnnotation()` method in `TypeDescriptor`
only supported a single level of meta-annotations. In other words, the
annotation hierarchy would not be exhaustively searched.

This commit provides support for arbitrary levels of meta-annotations
in `TypeDescriptor` by delegating to `AnnotationUtils.findAnnotation()`
within `TypeDescriptor.getAnnotation()`.

Issue: SPR-12793

Add StreamConverter to provide full support for converting
java.util.stream.Stream instances to and from collections or arrays.

Also attempt to convert the element type if necessary.

StreamConverter is registered by default in the DefaultConversionService
as long as Java8 is available.

Issue: SPR-12175

Issue: SPR-12578

(cherry picked from commit acefd838)

Issue: SPR-12297

Issue: SPR-11898

Issue: SPR-11608

Fixed through falling back to the raw parameter type in the TypeDescriptor(MethodParameter) constructor, properly detecting the vararg array even in case of an unresolvable type variable, and through restoring getElementTypeDescriptor's original behavior for arrays, i.e. always returning a non-null descriptor.

Issue: SPR-11494

GenericConversionService matches converters by full generic target type, allowing for the registration of multiple converters from the same source type to different collection types

Issue: SPR-11369

Issue: SPR-11354

Change the previously package scope TypeDescriptor constructor to
protected and add a getResolvableType() protected method.

Issue: SPR-11303

Issue: SPR-11225

Issue: SPR-11242

Add getSource() method to ResolvableType and TypeDescriptor allowing
access to the underlying source field or method parameter when possible.

Primarily added to provide access to additional type information or
meta-data that alternative JVM languages may provide.

Issue: SPR-10887

Restore the ability to create a TypeDescriptor for a collection or
map where the generics may be null.

Issue: SPR-11006

Refactor TypeDescriptor to use ResolvableType in order to retain full
generic type information, in the process fixing MultiValueMap support
in MapToMapConverter.

Issue: SPR-9499

Issue: SPR-10631

Issue: SPR-10130

- fix @since version in array()
- format method-level Javadoc
- unescape HTML-escaped angle brackets with {@code} blocks

Add a static factory method that can be used to create an array
TypeDescriptor with a specific element type. Allows array types
with generic elements to be constructed.

Issue: SPR-9792

Issue: SPR-10128

Content:

 - Rename Conditional{Conversion=>Converter}
 - Add @since tags where appropriate
 - Update Apache date headers to read 2002-2012 (not just 2012)
 - Correct minor Javadoc typo

Style:

 - Polish line breaks / whitespace
 - Use wildcard static imports where appropriate

Issue: SPR-9566, SPR-9692, SPR-9928, SPR-9927

Refactor internal workings of GenericConversionService in order to
better support future enhancements. This commit should not affect
existing behavior.

Issue: SPR-9927

- Use generic typing for getAnnotation()
- Add hasAnnoation() method
- Update existing code and tests to make use of changes

Issue: SPR-9744

- Remove trailing whitespace
- Apply consistent JavaDoc formatting

Before this change there were numerous javadoc warnings being reported
while building Spring framework API.

This commit resolves most of the javadoc warnings, reducing the total
number from 265 to 103.

Issue: SPR-9113

This renaming more intuitively expresses the relationship between
subprojects and the JAR artifacts they produce.

Tracking history across these renames is possible, but it requires
use of the --follow flag to `git log`, for example

    $ git log spring-aop/src/main/java/org/springframework/aop/Advisor.java

will show history up until the renaming event, where

    $ git log --follow spring-aop/src/main/java/org/springframework/aop/Advisor.java

will show history for all changes to the file, before and after the
renaming.

See http://chrisbeams.com/git-diff-across-renamed-directories

renamed mapKey/ValueTypeDescriptor methods back to getMapKey/ValueTypeDescriptor (for Spring 3.0.x compatibility)