Add back grain supplier to grain model

Need to remove token input fields from grain supplier,
 as the relationship is now defined from the grains
Add grain supplier to grain show view
Add hop_supplier and year to hops
Remove ability to set relationship from suppliers

Can no longer specify which hops/grains are associated to
suppliers in the supplier page.
This no longer makes sense as we are uniquely identifying hops/grains
by supplier.
Add relationship validation to hops/grains
Merge branch 'master' into hop_grain_model_changes
Fix misnamed hop_grain_supplier in hop model
Fix straggling 'N'
Seed things in accordance with the new requirements, add seeds for mash types
Merge branch 'hop_grain_model_changes' of github.com:stepheno/brewtronic-5000 into hop_grain_model_changes