On writes, option to omit trailing blanks and nulls

```
Where an array being written contains nulls or blanks, all are written as empty 
fields:

Current:  1,2,3,,,,,,
          1,,,,,,,,
          1,2,3,4,5,6,7,8,9


Wanted :  1,2,3
          1
          1,2,3,4,5,6,7,8,9



```

Original issue reported on code.google.com by `canw...@gmail.com` on 2 Dec 2013 at 8:58
