Support for per-getter formats and Calendar class

[charvolant]

At the moment, the only way to get something formatted as a date is for the getter to return a Date object.

I have a number of date/time instances across different timezones, where I need to put the date/time value into the spreadsheet as a double reflecting the localised date/time. (eg. A sighting at 2016-12-02T00:23:00Z should appear in the spreadsheet as 2016-12-02 10:23:00 if the sighting is in Brisbane and 2016-12-02 08:23:00 if the sighting is in Perth)

Ideally, I would like to implement a Getter that is able to specify the format of the cell that the getter fills. However, I would also like to be able to use the Calendar class that POI supports.