Selectable input updates

When using "bulk" update any individual values of  "null" will not get
updated whilst any numerical value inc 0 will update. This enables
selective input updates by "placing" any value(s) in the correct
position and order using  "null" entries eg
[[1409566580,10,null,20,null,40]] will update node 10 input 2 to 20 and
4 to 40 without effecting inputs 1 , 3 or 5+.
Merge pull request #268 from pb66/master_with_value_omission

Selectable input updates