Fix scrutinzier dependency retrieval

before_commands no longer work. Instead we override the dependencies step to include the developer dependencies we want.
Remove —-prefer-source.

Composer can toggle between list and source if one or the other fails.
Use local version of PHPUnit for scrutiniser tests
Add new proxy setting to use with SoapClient and when loading XSDs

- Add new configuration option and normalization
- Added unit tests
Merge proxy options into soapClientOptions configuration.

This ensures that the proxy configuration is used during both code generation and subsequent service calls.
Code cleanup

- Reformatting
- More error handling
Do not require the proxy_ prefix for proxy option keys.

proxy is already included in the option name. Instead we prepend it during normalization.
Add documentation of proxy option to README.