Extend separate_groups options in PropertySortOrder

[Alexander Bakhurynskyi]

If separate_groups is set to true and I have many groups defined in the order configuration, and some CSS selector has many single rules from each of the groups, it gives not the best looking result:

.item {
  position: relative;

  display: block;

  font-size: 1.2rem;

  color: #fff;

  cursor: pointer;
}

It would be great to have an option to suppress separation for one-liners and let them group with the other ones next to them:

.item {
  position: relative;
  display: block;
  font-size: 1.2rem;
  color: #fff;
  cursor: pointer;
}

.item {
  position: absolute;
  left: 50%;

  display: block;
  font-size: 1.2rem;
  color: #fff;
  cursor: pointer;
}