Offer to fetch QIDs before syncing citations

[diegodlh]

Right now source items without a QID are ignored by Citations.syncItemCitationsWithWikidata. Similarly, local citations with unknown-QID target items are ignored as well; i.e., not uploaded to Wikidata (although a Wikidata OCI may be added to them by SourceItemWrapper.addCitations if its PIDs match with that of the target item of one of the citations retrieved -#25).

Therefore, the safest flow would be to:

1. fetch QID for all source items
2. fetch QID for all target items
3. only then sync citations

To make it more friendly, the syncItemCitationsWithWikidata may offer the user to run both 1 and 2 at the beginning. In this case, maybe only safest matches (i.e., single matches from PID queries, vs multiple matches #34 or title-query matches #32) should be kept, and creation of new entities for QIDs not found (#33) should not be offered.