Vertically align content in Model and Parameters panels
Adjust droplist styles to match textboxen

The heights now match.

The text in the droplist (select box) is vertically aligned on Chrome,
but not on Firefox. To middle-align the text on Firefox, I added
padding-top, which is ignored on Chrome. See:
http://stackoverflow.com/questions/5439782/i-want-to-vertical-align-text
-in-select-box