don't pre-stringify display fields when saving user pref
update readme, add exlib readmes
fix breadcrumbs title updating, allow config base breadcrumbs
allow file upload from non-zotero domains

Requires setting Zotero.config.CORSallowed to false.
Makes best effort at upload, waiting for request to complete before registering
but cannot get response code from upload so registration could be erroneous.
closes #17
Merge pull request #19 from kimisgold/master

A shipment of margin adjustments
Adjust positioning of name field icons.
Give form elements default font size.
Adjust edit item form margins.