Add interceptor to resourceHandlerMapping

The resourceHandlerMapping in the MVC Java config is not configured
with any interceptors, and in particular those added through the
InterceptorRegistry, which are otherwise added to all other handler
mapping beans created by the config. This means that the
ResourceUrlProviderExposingInterceptor (added in 4.0) is also not
used for resource requests.

This change ensures the ResourceUrlProviderExposingInterceptor is
configured on the resourceHandlerMapping.

Issue: SPR-12279
Consistently accept empty Content-Type header and empty character encoding

Issue: SPR-12173
Polishing
EclipseLinkJpaDialect passes custom isolation level on to EclipseLink's DatabaseLogin configuration

Issue: SPR-12319
Improve HttpSessionHandshakeInterceptor

Use explicit flag whether to copy all attributes.
Check for duplicate keys in YAML map nodes

Snake YAML allows for duplicate keys in map nodes. See
https://code.google.com/p/snakeyaml/issues/detail?id=199

This commit uses a dedicated Constructor extension that explicitly
checks for such duplicate keys.

Issue: SPR-12318