Fixing assumed dependency issue; address minor build issue with tests in that the package name and file location were not in sync
Removed odd characters from pom which was preventing build.
Rearranged this so that the annotation stays on the get method (not sure it makes any difference - but this matches the rest of the class at least).
Returned file to original formatting so that we could see the details of this change (via git diff 4e68f577f02f58f9981bbcbd4b40367a3bd3033e src/main/java/com/softlysoftware/jxero/core/Invoice.java) ... the new amountDue property.
Happy to have the BigDecimal setter, but changing this base property to be a double purely to match the totals already in LineItem. Happy also to take arugments on changing them all to be BigDecimal - but would like to keep everything the same either way.