Item type switching

[avram]

Switching item types is hard to do-- we'll need to cache the item type mappings from the server, and use them to create conversion routines from one type to another, with confirmation when we're going to lose fields. This needs to happen ASAP, since we currently change the item type without changing the available fields. Maybe the conversion logic can be adapted from the Zotero client code.

[fcheslack]

A method for this is planned for the api as zotero.org also needs this (currently it just does direct field mapping and doesn't even warn on missing data). Not sure when that will be implemented though.

[avram]

This isn't too hard to do locally with cached item templates, but it'd be good to have the server handle, since this is a pretty complex task that requires serious understanding of the type system.

[avram]

The logic is here: https://www.zotero.org/trac/browser/extension/trunk/chrome/content/zotero/xpcom/data/item.js

[avram]

Pushing to 1.2 for now.