Content hashing

Entity hashing is done in content_hash#getEntityHashes.

It works by looking at the entity_changes table and going through each of the entity names/types:
- blobs
- attributes
- revisions
- attachments
- notes
- branches
- etapi_tokens
- options
For some reason note_reordering entities are ignored specifically.
All the rows in entity_changes are then ordered alphabetically, based on their entityId.
Every entity row is then grouped by entityName and then by sector. The sector is defined as the first character of the id.
The hash is altered to add the isErased value as well since the hash of deleted entries is not updated.
For each sector, the hash is calculated using utils.hash, using SHA1 encoded as Base64.