migrate auxotrophies to a table genetic_markers

We can store all genetic markers in a table, with columns:

• id
• name
• species_id
• gene
• allele
• comments

and then make a manyToMany relationship with the strains. Ideally, subsetting on the relevant species. This will cover auxotrophies and Mating types for yeast strains. It will also include markers of other species (C. elegans etc...) in the future.

I see this as a secondary implementation (after we have imported gylab database)