Introduced 4.0 versions of all XML configuration schemas

Removed spring-beans.dtd (the 1.x variant) and spring-oxm-1.5.xsd (pre-Spring-Framework variant), in order to raise the backwards compatibility limit a little bit at least. We'll keep supporting the 2.0 and 2.5 xsd versions for the time being, as well as spring-beans-2.0.dtd.

Removed the ref 'local' attribute in spring-beans-4.0.xsd since 'local' lost its differentiating role to a regular bean ref back in the 3.1 days when we started allowing for the same bean id to reappear in a different beans section of the same configuration file (with a different profile).

Issue: SPR-10437
Removed parsing support for the 'singleton' attribute in an XML bean definition

Following the introduction of spring-beans-4.0.xsd and the corresponding removal of the pre-2.0 spring-beans.dtd.

Issue: SPR-10437
Removed JDK 8 workaround (not necessary anymore with build 88)
MappingJackson(2)MessageConverter needs to use bean ClassLoader
MappingJackson(2)HttpMessageConverter alignment