Fix issue with useBeanValidation

Created by: UnklePig

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 and ./bin/security/{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\.
• Filed the PR against the correct branch: Default: master.
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Description of the PR

The useBeanValidation was not being set correctly in certain instances. In particular, when the default was set to true, in several languages it was impossible to set it to false. In addition, the help message was always saying the default was false, even when it was actually true - which could be confusing.

This fix has updated the CliOption class to add a method for assigning a default value when creating a boolean CliOption and called this from various places to ensure that the default is set correctly. It also modifies the code for the languages that were failing so that setting the value to false is handled correctly.