Bug 695610 - GnuCash Tax Invoice for Australia

This commit defines a new report called "Australian Tax Invoice"
which is the normal "Tax Invoice" with some changed default values.
These changed defaults have been filtered out of the the patch
that was attached to the above bug.

Not all changes have been picked. For example the two changed fonts
have been ommitted because they are not available on all platforms.

Also due to a bug introduced in commit 7015cf9edf312069aaab0028a1d9ac217cb8b43f
some options are now hard-coded. These include the report title,
the notes and the invoice number text.