Create follow-up e-mail after updating node

Problem/Motivation

When a node is created, the e-mail is sent. However, when a node is updated, no e-mail will be sent, despite the option to include it in subscriptions.

Steps to reproduce

Create a node. Update the node.

Proposed resolution

When nodes are updated, always sent notifications when the option is set. A user may disable the option to not create e-mails when updating. (A rule can be created to disable the option after the node has been created, so that there is no e-mail when updating a number of times accidently).

Remaining tasks

User interface changes

API changes

Data model changes