[security:medium] XSS on register form

In register form, we do not check XSS attack before registering data into session:

        # Use submitted value
        $req->data->{registerInfo}->{mail}      = $req->param('mail');
        $req->data->{registerInfo}->{firstname} = $req->param('firstname');
        $req->data->{registerInfo}->{lastname}  = $req->param('lastname');
        $req->data->{registerInfo}->{ipAddr}    = $req->address;

This allow to inject HTML code in form that will be displayed in mail for the end user, and can lead to malicious information (redirection on a hacker's site).

We should check for XSS before registering data, for example:

        # Check input
        if ( $self->p->checkXSSAttack('mail', $req->param('mail') ) or $self->p->checkXSSAttack('firstname', $req->param('firstname') ) or $self->p->checkXSSAttack('lastname', $req->param('lastname') ) ) {
                $self->logger->error("XSS on Register form");
                return PE_MALFORMEDUSER;
        }

        # Use submitted value
        $req->data->{registerInfo}->{mail}      = $req->param('mail');
        $req->data->{registerInfo}->{firstname} = $req->param('firstname');
        $req->data->{registerInfo}->{lastname}  = $req->param('lastname');
        $req->data->{registerInfo}->{ipAddr}    = $req->address;

A review on all public form should be done to check we have on other issues.