Add @ConditionalOnJava

Added a new @ConditionalOnJava annotation that allows to conditionally
enable configuration based on the Java version that is running. 

The annotation currently supports two modes of restricting Java versions:
the default mode checks for a Java version equal or better than the
requested one. Beyond that it can be configured to only match if Java
version is older than the configured one.
Add auto-configuration for Jackson's JodaTime and JSR-310 modules

We now register the Jackson JodaTime module with Jackson ObjectMappers
if it is on the classpath. We also register the JSR-310 module if it's
on the classpath and the application is running Java 8 or better.

Extracted the Jackson specific configuration previously residing in
HttpMessageConvertersAutoConfiguration into a JacksonAutoConfiguration
class.

Added the Jackson JSR-310 module as a managed Boot dependency.