Food group slugs contain special characters

[oliverroick]

The slugs for food groups contain special characters so they can't be used in CSS classes in the frontend.

           name           |           slug           
--------------------------+--------------------------
 Vegetable Oils           | vegetable_oils
 Meat                     | meat
 Spices                   | spices
 Pulses                   | pulses
 Fruits - Excluding Wine  | fruits_-_excluding_wine
 Fish, Seafood            | fish,_seafood
 Sweetners                | sweetners
 Starchy Roots            | starchy_roots
 Alcoholic Beverages      | alcoholic_beverages
 Animal Fats              | animal_fats
 Stimulants               | stimulants
 Treenuts                 | treenuts
 Milk - Excluding Butter  | milk_-_excluding_butter
 Vegetables               | vegetables
 Offals                   | offals
 Eggs                     | eggs
 Cereals - Excluding Beer | cereals_-_excluding_beer
 Oilcrops                 | oilcrops
 Sugar Crops              | sugar_crops
 Fruits, other            | fruits,_other

To make the slugs compatible with CSS naming conventions, I suggest to:

• Convert to lowercase
• Remove all special characters
• Replace white spaces with n-dashes (-)
• Conflate any subsequent n-dashes to just one

For example:

• Fruits - Excluding Wine becomes fruits-excluding-wine
• Fish, Seafood becomes fish-seafood
• Milk - Excluding Butter becomes milk-excluding-butter