Apply deid recipe actions to private DICOM tags

[wetzelj]

As discussed within PR #112 (comments), expand the list of fields evaluated to include private tags. This should enable recipe actions to be defined and applied to private tags in the same manner as they can be applied to public tags.

Since private tags do not have an assigned Name, these will have to be identified using the DICOM tag numbers.

[vsoch]

Yes! And we'll also need to better account for types. Most private tags can be indexed with their tag object, but when it comes to assigning some new value, we can't just throw in a string like we would for something like PatientID. This is similar to the function assignment issue, but more common for tags because it's never a simple string, but usually another Data Element.

[vsoch]

This is definitely done! Please open a new issue if anything comes up.