Core: remove dive->downloaded flag

This flag had two distinct uses:
 - signal that dives were downloaded, not imported
 - use to mark imported dives

Both are not used anymore, therefore remove the flag.
The uemis downloaded misused the flag to mark deleted
dives. Instead misuse the "hidden_by_filter" flag.

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>

core/liquivision.c

@@ -427,7 +427,6 @@ static void parse_dives (int log_version, const unsigned char *buf, unsigned int
 		}
 
 		// End dive
-		dive->downloaded = true;
 		record_dive_to_table(dive, table);
 		dive = NULL;
 		mark_divelist_changed(true);