Add filters and options for restaurant menu items.

[briancwelch]

Since we are requiring this plugin as the base: https://wordpress.org/plugins/restaurant/, we are going to need to add additional post data and also add some options for how the data is displayed.

Currently the plugin only supports the output of menu prices in USD, however the dollar amount is static, and we can offer an option for the user to select which currency type is to be displayed using the customizer.

It would be preferred to find a method that retrieves worldwide currency types via API and populates the select box with the data. That way, we do not have to hard-code in specific currency types to be selected and can support all known currencies that restaurants may use.

We may also need to add additional filters, such as if a menu item is gluten free, allergen info, etc.

[briancwelch]

Looks like we might be able to use this: http://www.freecurrencyconverterapi.com/api/v3/currencies

[briancwelch]

See method (needs fix): https://github.com/presscodes/maera-restaurant/blob/master/includes/class-Maera_Restaurant_Data.php#L72-L95

[briancwelch]

Fixed in 3040bd4