Add ability to make Prep Counts dependent on other prep counts

[tlammer]

Requested by Ohio Mollusks

They would like to be able to set up rules where the count on one prep record would change depending on how the count on another prep record is altered.

For example, they have prep types similar to 'whole specimen', 'shells only', and 'soft body'. If they take apart the whole specimen and manually decrease the count by one, they will always have the shell only and soft body counts both increase by one. They would like that increase to be automated.