Private message refactoring: fix up various template issues. Added a template tag to generate the URL to send a PM to a user. This replaced the {% url 'messages-compose_to' username %} in various templates.

.poll-form {
    padding-bottom: 1em;
}
.poll-form ul {
    list-style: none;
    padding-bottom: 0.5em;
}
.poll-form li {
    padding: 0.5em 0 0.5em 0.5em;
}
dl.poll-result {
    width: 80%;
}