We need more linking tables for the eimage table

[dsenalik]

I propose adding linking tables from the eimage table to organism, stock, and biomaterial for germplasm etc. images, and to project, study, and analysis tables to handle images resulting from any sort of investigation. Are there others?

I further propose including type_id and rank columns, for example, to distinguish between "flower" and "leaf" images, and allowing ordering the images as needed.

Apparently there is much earlier discussion about this https://github.com/GMOD/Chado/issues/31