User sheet breaks if user has special characters set as their first/last name

The first and last names in the user profile are not escaped for xwiki syntax, so `~` are not displayed, and if a user has a name like `]][[` and `]] info [[`, the user profile section will be hidden. (the 2 names behave differently)

The behavior is different when viewing as the user: (14.10 only)

And as superadmin:

The user can still edit the page using the regular edit button instead of the top-right edit button in the missing profile section.