Should we use the ConversionTrigger Type on both Convertibles AND Warrants

[JSv4]

On our Convertibles we have a ConversionTrigger type which we use to track under what conditions a convertible is eligible to be converted (and this use will be much cleaner and clearer if my latest PRs are merged). It strikes me we might want the same data structure for Warrants. Currently, the WarrantIssuance lets you specify StockClassConversionRights in its conversion_rights field, but these only let you describe how to calculate the conversion amounts, not under what conditions, and this seems less expressive and, IMHO, less suitable than a list of ConversionTrigger types.

[JSv4]

Incorporated into changes in PR #175