Refactor to use Symfony Console component instead of custom CLI code.

This brings more features and allows us to focus one the core functionality of the app.

- Replace custom CLI code with Generate console command maintaining mostly the same signature
- Added support for PSR3 compatible logging in Generator and implement a logger for console output
- Move main application from generate.php to wsdl2php.php
- Remove obsolete CLI code and tests
Replace Symfony with Composer for class loading.

This reduces the dependency chain.