[Namespace Cleanup] Huge namespace rework.
- Definitions and Helpers namespaces are gone in favor of more specific namespaces such as Folders, ContentTypes, Fields, Pages, Documents, Sites, etc.
- FieldTypes namespace merged into new Fields namespace (built-in OOTB field info constants moved from root Dynamite namespace to Fields.Constants)
- MasterPages namespace merged into Branding
- Utils and Repositories namespaces's content narrowed down a lot