amend/update Working properly

update_fields removed - this just won't work as we're saving new rows.
If it's truly needed we can use it as a list of fields to copy from self
to old_self to limit what gets saved, but the query efficiency it was
created for will be lost.

amend() now writes three rows again. This is the correct behavior

Test setup fixed to have consistant transaction time.

[#63421322]
delete implemented

End old transaction
write new open transaction with valid_end_date set

[#63076858]
Delete improved and documented

Created eradicate() function to really delete rows. This is unexpected
behavior in a bitemporal table, but the test driver does need to remove
rows.

Delete may only be called on current objects
Delete will not set new transaction times on self, but will return the
new row

[#63076858]
Tests for delete

Deleting a non current object fails
Deleteing a current object does not remove it from the table

[#63076832]