Add warning flags for certain classes of product

[sebbacon]

• potential bioequivalence issues (with a note that things may not necessarily be substitutible - see #8)
• list (or count) of available pack sizes with flag (with a note about how pack sizes can effect price and there's not much a GP can do)
• specials and imports (with a note that they are often very variable in price and there's not much a GP can do)
• special containers (with a note that these may be prescribed by the pack)
• NP8 can be highlighted re. the gouging issue