`vss0` constructor: table-level options

[asg017]

create virtual table demo1 using vss0(
  factory="IVF4096,Flat,IDMap2",
  metric_type=L1,
  a(100),
  b(100),
  c(100)
);

create virtual table demo1 using vss0(
  factory="IVF4096,Flat,IDMap2",
  metric_type=L1,
  a(100) factory="Flat,IDMap2",
  b(100) metric_type=L2,
  c(100)
);