Support util function to convert an XML string into a note object

[melisabok]

The implementation is placed here: https://github.com/openreview/openreview-py/blob/master/openreview/profile/process/dblp_transform.js

It should be called from the UI before posting the note using the API 2, the resulting note should follow the API 2 spec.

[carlosmondra]

Fixed with #23