Made compatible with the Delivery SDK v14

[petrsvihlik]

Motivation

Made compatible with: https://github.com/Kentico/kontent-delivery-sdk-net/releases/tag/14.0.0-rc1

Checklist

• [x] Code follows coding conventions held in this repo
• [x] Automated tests have been added
• [x] Tests are passing
• [ ] Docs have been updated (if applicable)
• [x] Temporary settings (e.g. variables used during development and testing) have been reverted to defaults