* Update Gradle in generated Java projects from 2.14.1 to 6.0.1
* Upgrade Java 11 native Gradle from 5.5 to 6.0.1
When Java 11 native client library was introduced it was introduced with an overridden version of the Gradle wrapper (5.5 instead of 2.14.1). From looking at that PR, there doesn't appear to be any specific reason for the versions to differ. This removes the only override of the Gradle wrapper so all the Java projects are up to date and shares the same version.
* Add support for Spring's RestTemplate in Java client codegen
Resolves#1176
* Update all Java samples to include change for Jackson enums
Currently enums are deserialized from a String value with an
explicit @JsonCreator. However, they are not being serialized with
this String value. This change introduces the @JsonValue annotation
on the toString() method of enums, so they will be serialized as a
String with the correct value.