Adds a clear warning when a user's selected timezone differs from their browser timezone. This helps users spot configuration mismatches that could cause appointments, deadlines, or activity times to appear incorrectly.

This update adds default accounting accounts needed for Canada payroll and corrects tax sign handling. It helps Canadian payroll setup work more reliably with the standard chart of accounts, reducing manual configuration for businesses.

This PR is related to https://github.com/odoo/odoo/pull/6465 for v8 and
https://github.com/odoo/odoo/pull/5351 for v7.

The Canada payroll is almost complete and will soon be merged to OCA, see https://github.com/OCA/l10n-canada/pull/43 and https://github.com/OCA/l10n-canada/pull/56. This pull request adds the default accounts for the Canada payroll.