Performance improvements needed for schema form editor

[jpfiset]

Schema form editor is demonstrating sluggishness when editing large documents. From observations, there seems to be one main reason for this issue: the schema form editor often refreshes the complete view. This happens under two conditions:

• when moving items in an array
• when changing the value of a custom type

[ahayes]

I tested this out and I noticed one bug where it seems the very first or last item, when moved, can’t be moved back again by their newly added direction arrows. It is not a show stopper since you can just move other languages instead or save and edit again, but I wanted to document it. I don't recall seeing that bug before these latest changes.