[IMP] account_chart_update: deletion of tax codes removed from templates

For tax codes, it make sense to propose deletion, since tax codes
are normally defined by the tax authority and the user does not
customize them.
[IMP] account_chart_update: compare more fields in tax codes
[IMP] account_chart_update: update accounts on taxes even if an update of the account was not requested

Useful when the chart of taxes changes but the chart of account
need not be updated.
[IMP] account_chart_update: depth-first search of tax codes

This helps creating parents before children.
[IMP] account_chart_update: compare more fields in taxes