Display name of users that make changes instead of number of users in activity macro

Examples:

• "3 changes by Ecaterina Valica" instead of "3 changes by one user"
• "2 changes by Ecaterina Valica, Sergiu Dumitriu and Vincent Massol" instead of "3 changes by 3 users"
• "2 changes by Ecaterina Valica, Sergiu Dumitriu and Vincent Massol and 10 other users" instead of "3 changes by 13 users"