avro

AVRO-3427: skip creation of namespace directories for csharp schema (#1578)

* Add new argument parameter --skip-directories. It will skip creation of directories for namespace. Just generate classes in output directory

* Add missing doc param description

* Fix Unit tests after merge with master

* Fix Unit tests after merge with master

* C# Add unit tests for --skip-directories option

Co-authored-by: Pawel Kordowski <pawel.kordowski@stepstone.com>