Code in the field alteration logic had a queries defiend as strings to
begin and commit transactions involve with changing table or column names.
This was causing fatal errors as BEGIN is not a valid keyword within
a trasaction (see SQLite documentation excerpt below).
A new api has been introduced to deal with transactions programmatically,
and this module was updated to support this a few months ago. This is a
tidy up of some missed portions - consuming this API which correctly uses
SAVEPOINT when a nested transaction is required automatically.
https://www.sqlite.org/lang_transaction.html
Transactions created using BEGIN...COMMIT do not nest. For nested
transactions, use the SAVEPOINT and RELEASE commands.
