Upload silently fails for example dataset

[alexsb]

This is a movies dataset in D3 JSON format. No response after a few minutes.

https://drive.google.com/open?id=1tGDHfAFnYhcGltE5hP2y0R-rHbePDqiq&authuser=alexander.lex%40gmail.com&usp=drive_fs

[jjnesbitt]

It seems the reason for this is that the provided file has ~100 entries in the nodesfield that are empty objects. The D3 JSON format used by multinet expects each node to have an id field, so these empty objects fail during parsing. However, this raises a few good points:

• If an object is found that doesn't contain an id field, that individual object should just be ignored, rather than the entire upload failing.
• The client should show that this upload failed, rather than forever waiting for it.
• The client should show the reasons for upload failure.

I can work to address these issues.