Bam 166 improve notification mechanism

[callapa]

Description

Create a event dispatcher manager service to allow form extension from modules.
Add a dynamic section (named 'contact.form') in the contact form to be used to add a new section.

Type of change

• Patch fixing an issue (non-breaking change)
• New functionality (non-breaking change)
• Breaking change (patch or feature) that might cause side effects breaking part of the Software
• Updating documentation (missing information, typo...)

Target serie

• 2.8.x
• 18.10.x
• 19.04.x (master)

How this pull request can be tested ?

With a Centreon fresh install, install the new version of BAM module.
Next go into contact section and open form to add a new contact.
A new section will appear for BAM.
Check if the section appears correctly.

Uninstall the BAM module and go back to the form to add a new contact.
The BAM section has left.

Checklist

Community contributors & Centreon team

• I followed the coding style guidelines provided by Centreon
• I have commented my code, especially new classes, functions or any legacy code modified. (docblock)
• I have commented my code, especially hard-to-understand areas of the PR.
• I have made corresponding changes to the documentation.
• I have rebased my development branch on the base branch (master, maintenance).

Centreon team only

• I have made sure that the unit tests related to the story are successful.
• I have made sure that unit tests covers 80% of the code written for the story.
• I have made sure that acceptance tests related to the story are successful (local and CI)