Seems like it would be nice to just support formats available via format Strings that String.format() uses.
Note that existing support for date/time values use different formatting; this should be fine, and if we want to for some reason support something from java.text.Format it should be possible to use heuristics to determine intended type of format. However that may not be necessary.

Initially we should just support simple types:

• java.lang.String
• int, long, short, byte, float, double and matching wrapper types
• BigDecimal, BigInteger