(#1860) - info.doc_count is wrong

This is a less ambitious version of #1860 that does not attempt to make leveldb any faster.  In fact we just stop using the `_local_doc_count` entirely, because it doesn't take deleted docs into consideration. Instead we just iterate through all the docs to give us `total_rows`/`doc_count`.

This does make IDB faster, and it makes both IDB and WebSQL correct.