show conserved physicochemical properties in conservation row

Certain tools, like Promals3D, give an indication of the type of physicochemical properties observed at each position in an aligned column. Whilst such information is reflected in the conservation annotation row, the actual properties that are present and conserved are not actually given. These properties could be extracted from the property conservation matrix and rendered as labels (or even as a logo) under/over the conservation annotation row, or shown as a conservation symbol along the lines of promals/Joy/Chroma (where bolding, upper/lower case and/or italics are used to indicate physicochemical conservation).

(suggested by David Karlin, Ox.)