Add MX and TXT records and Allow editing of multi-value records such as A records

change the change function to take either a single string for value or
a sequence of values and generates the appropriate record sets.

The extra 1 in (zf-xml/xml1-> rr :ResourceRecords :ResourceRecord :Value zf-xml/text)
prevented deleting multi-value records because the values where trunkated causing
amazon to reject the request.

also starts a new -SNAPSHOT release cycle