Apply the new design on the room avatar and name

[giomfo]

1- The expected changes on the room avatar are presented by:

• the padlock icon is now grey (#4f4f4f) and moves to the top right corner of the avatar
• a new icon is added at the top right corner of the forum avatar
• we will not apply the suggested border on the avatar of the unrestricted rooms (opened to external users). We will keep the light grey border.
• for the restricted rooms, we will keep the thin border. We will change the color of this border by using the same grey (#4f4f4f) as the icon.
• these changes on avatar display will be applied on all the screens: rooms list, room titles, forums list

2- About the rooms list, we will add a coloured label "Privé", "Forum" or "Externes" at the top right corner of the cell

3- In the room title, we will update the the sub-title by adding a coloured label "Salon privé", "Salon forum" or "Salon privé ouvert aux externes". The existing third title line will be used only for the potential room retention period.