CustomFieldType API needs to allow for a "needsMove" type method

This is related to JRA-10213. Once this is done we should be able to remove the hack that was put in place to resolve that issue. I have left this a bit open-ended since there are a number of ways to solve this issue. The end result should be that a custom field can look at the IssueContext of where it will be moved and at its current location and determine if its values will need to be updated for a correct move to occur.