ParamConverterProviders should allow format strings if applicable

[smoyer64]

Many ParamConverters assume a default String representation for a specific Java type. Right now, we've standardized on ISO-8601 for Date, Time and Timestamp formats which aligns with the new Java Date/Time library. In the event we have to process other String representations, we should have the ability to customize these converters - two annotations immediately come to mind but there may be more:

1. @FormatString - Allows the user to specify an alternate format string (for conversions that accept one) or to specify the format string for conversions that require one.

2. @DefaultTimeZone - Allows the user to specify the time zone to be used if one is not included with the ISO-8601 compliant string. This allows what would otherwise be LocalDateTime objects to be Instant or ZonedDateTime.