new script syntax: setting options of children

Change one of tests to use this feature.

Example:
Write {target=target, skip_rest=true}
                      ^^^^^^^^^^^^^^
block.gc = -1 if no A,T,G,C in the block
move pangenome.bs to dir pangenome/
move pangenome.ba to dir pangenome/
rename global-blocks/pangenome.% to %/blocks.%
move features.bs to dir genes/
move pangenome.* to pangenome/
BlockInfo: add option count-genomes