Create utility to clean up duplicate data files

[LiefEsbenshade]

Feature:
If a user saves multiple identical versions of a datafile with different stamps we should delete them to conserve disk space.

Problem:
This is more complex than just running a comparison and deleting. If the user has commits with data_vc pointing to the deleted file then the read functions will fail if the user ever returns to that commit. We can't alter commits. Additionally, we can't change data_vc (e.g. to add an alias) because data_vc will revert to its prior state when the user goes back in the git history and any insertions to note the 'delete because identical to x' will be lost.