Support for storing recurring blocks

[vanderhe]

In order to be able to replace the old HSD Python implementation in the SkProgs suite, it would be nice to add support for defining recurring blocks, e.g.

$OCCUPATIONS_Ne {
  1S = 1.0 1.0
  2S = 1.0 1.0
  2P = 3.0 3.0
}

[samtsevich]

@aradi
Is that possible to solve this issue with low effort?