[Java][jersey2]: Documentation changes and making example snippet compilable

[saigiridhar21]

PR checklist

• Read the contribution guidelines.
• Ran the shell script under ./bin/ to update Petstore sample so that CIs can verify the change. (For instance, only need to run ./bin/{LANG}-petstore.sh, ./bin/openapi3/{LANG}-petstore.sh if updating the {LANG} (e.g. php, ruby, python, etc) code generator or {LANG} client's mustache templates). Windows batch files can be found in .\bin\windows\. If contributing template-only or documentation-only changes which will change sample output, be sure to build the project first.
• Filed the PR against the correct branch: master, 4.1.x, 5.0.x. Default: master.
• Copied the technical committee to review the pull request if your PR is targeting a particular programming language.

Description of the PR

Closes: #3059
Closes: #3060

For Java Jersey2's client, following changes are done.

• Adding Http response details on each method's summary.
• Adding Http response details on the api docs (Jersey2 is using common api_doc.mustache and so other client's petstore projects were also update in this pull request).
• On api docs, example snippet was updated to make it compilable.
• On Readme, example snippet was updated to make it compilable on Readme(Jersey2 is using common readme.mustache and so other client's petstore projects were also update in this pull request).

@bbdouglas (2017/07) @sreeshas (2017/08) @jfiala (2017/08) @lukoyanov (2017/09) @cbornet (2017/09) @jeff9finger (2018/01) @karismann (2019/03) @Zomzog (2019/04)