More doc for Extension update

[tdipisa]

Description

It would be good to enhance this section of the online documentation to better explain how to update an extension already installed along with all relevant considerations concerning its configuration.

Documentation section involved

• [ ] User Guide
• [X] Developer Guide

Other useful information

[alexander-fedorenko]

@tdipisa We have similar content about extensions management available both in user-guide and developer-guide, so I've added a section with update instructions in user-guide and referenced it in developer guide.