- Add code to create two new AvaTax DB tables
- Add code to populate tables on queue processing

- Remove code that is now unused
- Add code to migrate data from old columns to new tables
- Refactor code to load data from new tables into ext attributes

- Add doc blocks
- Revise code to remove unused methods
- Add upgrade data script

- Remove code for Refund plugin
- Add code to remove unused AvaTax columns from core tables
- Refactor code so new install will create new tables instead of adding
  columns to core tables

- Revise code to utilize magic getters and setters
- Revise code to utilize constants for column names
- Remove unnecessary methods

Removed backslash in fully qualified use references

…und-to-store-credit

# Conflicts:
#	CHANGELOG.md

- Revise version number in appropriate locations

…instead of “NULL” values

…ith “0” instead of “NULL” values"

- this change is actually not needed, since each invoice should always record values, even if it’s not imbalanced

This reverts commit 8fe14e8.