Add Company/Vendor specific XSD Files for the XSD Validation

[dlabordus]

User Story
Make it possible to add company/vendor specific XSD Files to the container. These XSD Files should be included in the XSD Validation process to make it possible to validate the SCL XML Private Sections for these companies/vendors.

Acceptance criteria
The XSD Validation process scans a specific directory for XSD Files to include these in the process and make it possible to validate private sections. The directory should become a Volume in the Docker Image to make it possible to add the XSD Files during deployment.