Expected Behavior
When a field contains an array as its value and is updated, the value returned by editValue should be presented to update_item in the same form.

For example, let's say we have an item that looks like this: {"fruits": ["apple", "banana"]}. Let's say that we edit the item such that the fruits field should only contain ["apple"]. In other words, editValue returns ["apple"]. Then, we would expect update_item to receive the argument {"fruits": ["apple"]}.

Actual Behavior
The value returned by editValue is corrupted before being passed to update_item.

In the example above, editValue returns ["apple"], but update_item receives {"fruits": ["apple", "banana"]}.

Steps to Reproduce
https://jsfiddle.net/jnooq68m/1/

1. Open console, to watch debug messages.
2. Click on row to edit it.
3. Click on checkmark to confirm save.
4. Even though editValue returns [1], the new value is set to [1, 2, 3].

Steps to Fix
This problem is occurring because of line 1444 in jsgrid.core.js (as of commit f521a20).

updatedItem = $.extend(true, {}, updatingItem, editedItem);

Because of the true in this call, jQuery performs the extend operation recursively. To fix this bug, we should make this extend non-recursive by changing the line to:

updatedItem = $.extend({}, updatingItem, editedItem);

A similar change must also be made on line 1455.