Consistent java.util.Optional resolution, lenient handling of optional multipart files, correct Servlet 3.0 Part list/array selection

Issue: SPR-13418
Issue: SPR-13849
Issue: SPR-13850
Issue: SPR-13893

Issue: SPR-13874

This is in line with the current behavior of HttpServlet that would
have been in used with dispatchOptionsRequest on the DispatcherSerlvet
set to false (the default prior to 4.3).

Issue: SPR-13130

The WebContentGenerator now maintains an additional property that
sub-classes can use for an "Allow" header in response to an HTTP
OPTIONS request. This property is pre-initialized once at startup
and does not have to rely on getSupportedMethods in addition to
adding HTTP OPTIONS if not explicitly listed.

Issue: SPR-13130

Issue: SPR-13585
Issue: SPR-12180
Issue: SPR-7915
Issue: SPR-8450

Issue: SPR-13879

Issue: SPR-12948

Issue: SPR-10660

Issue: SPR-10202

Issue: SPR-13844

Issue: SPR-13845

Issue: SPR-13130

Issue: SPR-13130

AbstractJackson2HttpMessageConverter now implements its own
TypeVariable resolution algorithm since in Jackson 2.7 it is now
deprecated and has not the same behavior .
See https://github.com/FasterXML/jackson-databind/issues/1087
for more details.

The dependency on jackson-datatype-jdk7 has been removed since
it is now provided by default in the jackson-databind module.

Issues: SPR-13483, SPR-13728

Issue: SPR-13130

Issue: SPR-13130

This commit updates the javadoc of
`RequestMappingHanderAdapter.setCacheSecondsForSessionAttributeHandlers`
to explain how one can disable that feature and prevent "Cache-Control"
directives from being added when `@SessionAttributes` annotations are
used on Controllers.

Issue: SPR-13598

Prior to this change, configuring a `FixedVersionStrategy` like so
would configure a single "/js/**" path pattern:

```
versionResourceResolver.addFixedVersionStrategy("v1.0.0","/js/**");
```

This commit makes sure that for each path pattern, its prefixed version
is added to the map. For example, the previous configuration also
adds "/v1.0.0/js/**".

Issue: SPR-13883

Prior to this change, the `RequestMappingHandlerAdapter` would first add
a "Cache-Control" HTTP header to the response (depending on its
`WebContentGenerator` configuration and `@SessionAttributes` on the
handler class); then, the Adapter would delegate the actual handler the
processing of the request.
This leads to issues, as the handler does not have full control to the
response and has to deal with pre-existing headers in the response. This
means that the Adapter and the handler can add incompatible
Cache-Control directives without knowing it, since one cannot see the
headers added by the other until the response is committed.

This commit switches the order of execution: first, the handler is
called (possibly adding HTTP headers), then the RMHA processes the
response and adds "Cache-Control" directives *only if there's no
Cache-Control header already defined*.

Issue: SPR-13867

This change exposes protected methods for instantiating sub-classes of
RequestMappingHandlerAdapter and ExceptonHandlerExceptionResolver
similar to the existing method for RequestMappingHandlerMapping.

Prior to this change SpEL did not have an syntactic
construct enabling easy access to a FactoryBean. With this
change it is now possible to use &foo in an expression when
the factory bean should be returned.

Issue: SPR-9511

Spring MVC Test now parses application/x-www-form-urlencoded request
content and populates request parameters from it.

This can be useful when running client-side tests against a MockMvc
via MockMvcClientHttpRequestFactory.

Issue: SPR-13733

Issue: SPR-13044

Prior to this change, the `ResourceUrlEncodingFilter` would try to
lookup resources URLs as soon as the given URL would be longer than the
expected context+servlet prefix path. This can lead to
OutOfBoundsExceptions when the provided URL does not start with that
prefix and still has the required length.

This commit makes sure that all candidate URLs for resources lookup are
prefixed with the cached servlet and context path. This underlines the
fact that the `ResourceUrlEncodingFilter` does not support relative URLs
for now and delegates to the native servlet implementation in that case.

Issue: SPR-13861

Issue: SPR-10087

Issue: SPR-13719

Prior to this commit, Spring MVC Test only supported HTTP methods GET,
POST, HEAD, OPTIONS, PUT, PATCH, DELETE, TRACE and multipart file
upload. This change adds generic methods to MockMvcRequestBuilders in
order to allow testing of arbitrary HTTP methods in a Spring MVC
application.

Issue: SPR-13719

Issue: SPR-13876

Issue: SPR-13560

This commit allows to create a Quartz trigger implementation via
either `CronTriggerFactoryBean` or `SimpleTriggerFactoryBean` even if no
job detail is provided.

Issue: SPR-13604

Issue: SPR-13837