Fix for deleting an item from non-unique index

[M1Les]

When an item is removed from the store, non-unique index it is part of, will be reset to undefined:

ind.remove will remove all values from the index, even if there are multiple items in that index (in case of non-unique index).

In this fix we're splitting remove operation in two steps for non-unique indices:

• Find the index value (array of items with the same index)
• Using primary key, locate and remove the item from the array

There are possibly some performance implications to doing array.filter to remove the item, but could not come up with a better way of removing item without iterating over all array items -- yes, we can stop comparing pks after the first match, but we still need to go over the rest of items to finish copying the array.

[M1Les]

Closing it in favor of #25