Added default disabled select option

Closes #37 (closed)

Unfortunately, Thymeleaf contains an issue where you cannot use th:field together with th:selected. It turns out wrapping the elements in div tags solves this problem, but yes this is an ugly work-around. See: https://stackoverflow.com/questions/24203220/thselected-a-number-in-a-select-option-with-thymeleaf-doesnt-work