PHP & Twig : Clean & standardize code

[AnnaigJegourel]

• [x] Use addslashes() to avoid apostrophe input error & clean useless comments in Controllers

Syntax & naming:

• [x] Update method names to standardize
• [x] Update Class Diagram
• [x] Update twig files (only one message file /factorize error & success messages)
• [x] Update form names to harmonize with methods names

Render / Redirect after CRUD actions:

• [x] Update methods order & visibility
• [x] Update this / self functions calls