Implement optional human-readable expansions of column names.

[bokov]

Have some sort of optional data dictionary or additional columns in an existing data dictionary that, if detected by server.R, provide some human-language interpretation of what the often terse and underscore-filled variable names are supposed to mean.

For the obesity data and studies like it, this already exists as the "Name" column in the REDCap data dictionary, we just need to use that information.

Then, need to figure out where the user would see it. Perhaps as tool-tips visible on mouse-hover. Or perhaps as text that dynamically appears while the corresponding column name is selected in the X and/or Y pulldown menu.