Make snapshot timeout configurable

Also increase defaults.  In riak snapshots may be used to fold over all objects, and with delays at the receiving end, this could take significant time

include/leveled.hrl

@@ -78,7 +78,9 @@
                         source_penciller :: pid() | undefined,
                         snapshot_longrunning = true :: boolean(),
                         compression_method = native :: lz4|native,
-                        levelzero_cointoss = false :: boolean()}).
+                        levelzero_cointoss = false :: boolean(),
+                        snaptimeout_short :: pos_integer() | undefined,
+                        snaptimeout_long :: pos_integer() | undefined}).
 
 -record(iclerk_options,
                         {inker :: pid() | undefined,