Add db.UniqueMixin and adjust pylint as necessary with new ignores
Add test for session cache clearing on new requests
Fix session cache state expiry
Add support and tests for rollback of UniqueMixin
Support auto-retry of _unique due to race conditions between query and add; Adds redo req
Give up on solving race, revert redo use
Fix unsaved file up
Add docs while sleepy... forgive typos
Copyedits
Merge issue-77 (PR #77) - fixes #77