Rename pages in left menu and titles

In left menu:

• "User" to "Users"
• "Roles" to "Users roles"

In page titles:

• "User" to "Users managment"
• "Roles" to "Users roles managment"
• "Groups" to "Groups managment"
• "Users" to "Requests managment" (Requests page)
• "Policies" to "Policies managment"

In page tabs:

• "User list" to "Users list" (Users page)