Add doc-typehints to class properties found by the PropertyDocumentation
sniff to improve the documentation.
Once the sniff is enabled it avoids that new code is missing type
declarations. This is focused on documentation and does not change code.
Change-Id: Idf17719c875466810313f0fbbf16bc67f3e40059
Add some of the basic REST API class hierarchies:
* EntryPoint
* Router
* Request
* Response
* Handler
The actual entry point file rest.php has been moved to a separate
commit, so this is just an unused library and service.
Bug: T221177
Change-Id: Ifca6bcb8a304e8e8b7f52b79c607bdcebf805cd1