Lock the entity only if the user has performed changes on the page

Problem/Motivation

Instead of locking the entity when its form is retrieved the entity should be locked when the user performs any change on the form in the browser.

Proposed resolution

1. Through JS detect if a change has is made and then lock the entity.
2. Inform other users that the content is locked if they are on the same edit form as well.

Remaining tasks

User interface changes

API changes

Data model changes