Aussie GST + Hours Patch

[Adam Iredale]

Hi,
     I have written (for personal use) a patch for invoice.scm that changes
the wording to comply with Australian Business Legal requirements for GST
etc.  I have also added another counter that tallies hours - for those who
invoice for services (like I do).  In my opinion this should appear as a
separate report in GNUCASH but I just tacked it on as so.  Would you like
the diff?

A.