Reformat Javadoc to add line wraps

[ash211]

I have an internal code generator that adds very long Javadoc using javapoet's MethodSpec.addJavadoc(). Unfortunately the generated output doesn't add line wraps, so the Javadoc is all on one very long line. I'd like this to be wrapped for improved readability, but there is no option for that library to set on goethe to reformat Javadoc as well as Java code.

Blocked on palantir/palantir-java-format#724