Optionally link recipe values to dates and/or camera formats

[eugene]

There are some recipe options which change for a given camera as a function of when the data was take. For example, before Dec 9, 2009, GPC1 data needed to be corrected with the "PATTERN" option (row-by-row pattern subtraction). After Dec 9, 2009, this is no longer needed.

Our basic recipe management system can only handle this by having different reduction classes for these two periods. However, this is not something whic gets automatically set.

We need to be able to specific that certain recipes, recipe values, or reduction classes should be valid in certain time periods.