Proper support for to_comment/from_comment

[RFSH]

Currently, to_comment and from_comment are only used in the related references.

We should investigate the other places (for example, aggregate columns) that should be using this. We should also make sure from_name and to_name are used consistently everywhere.

P.S. We found this while working on the annotation for functional_assay_handbook table in RBK/GUDMAP. The comments were defined on a foreign key, and we were expecting ermrestjs/chaise to use those on an array aggregate. But ermrestjs/chaise is currently using the table's comment and now we have to define redundant comments in multiple places.

[RFSH]

This came up before as part of #852