* Closes#5863
The "dateLibrary" option for java, sadly, sets a mustache value "java8". This change updates this so that "java" in the mustache
libraries means what it should mean - use all java8 classes. In this case, there's no need for the third party Base64 library
as java8's JDK has this built in. In my view, the "dateLibrary" should be deprecated but that should be a separate PR.
* Closes#5954
built and ran tests/samples
* [feign] add threetenbp support for feign clients
* [okhttp] add threetenbp support for okhttp clients
* [jersey] add threetenbp support for jersey clients
* [retrofit2] add threetenbp support for retrofit2 clients
* [spring] add threetenbp support for spring generators
* add a workaround in tests for a bug in the petstore
The petstore doesn't manage fractional digits of dates correctly when there are less than 3
by fixing the logic of enum Boolean checking.
Other changes:
* Remove the `true &&` prefix from the `equals` method in models.
* Apply some changes of Java-default to Java-okhttp-gson, i.e. adding
`this` and parent model handling.
* Some improvements on spaces and blank lines.
