* Importer will now ask user for a login and password via form and will
perform sign-in directly using credentials rather than oauth
* Signing in this way enables importer to obtain desktop document ID
which is now stored for each item
* It's possible to switch back to the old method (ouath) by setting
`import.mendeleyUseOAuth` pref to `true`.
* New option to only import new items. This options only appears if
database contains previously imported items.
* Importer will now update mendeleyDB:documentUUID on existing items to
match value used in Mendeley Desktop if available
* Importer will no longer create collections when no new items are
imported * Importer will only report number of new items imported on
re-import * Importer will now preserve dateAdded on re-import
Co-authored-by: Dan Stillman <dstillman@zotero.org>
