Revert "Introduces a JSON serialization for Page: pages"

The change introduced various issues because the JSON serialization is sometime saved in the database.

This reverts commit 1bd97d9bcda3337f25f5c4ed67e2dc852dbe7806.

Change-Id: I3872d9ad1188a6f32300dc617ce864c9fe643e84
Merge "Revert "Introduces a JSON serialization for Page: pages""