data, help: show path examples beside the tree

[karalabe]

ark data paths printed the tree alone and left the example values to --json. Placeholders such as <chr> and value files such as genotype read better with a sample beside them, and the tree is narrow enough to leave room at the side.

Render each entry's examples in one column two cells right of the widest row, muted and joined by commas. Rows without examples stay as they were. Long lists wrap through the existing wrap helper with the hanging indent at the column, so continuation lines stay inside it.

  v1/genome/ +
    positions/ +
      <chr>/ +             chr1, chrX, chrM
        length             248956422, 16569
        <pos>/ +           5227002, 1
          reference        T, ATCG
          genotype         A/G, T|T, A, ./., A/., ., AT/A, T/*, A/<DEL>
    genes/ +
      <gene>/ +            BRCA1, TAS2R38, HLA-A

Extend the hierarchy test with examples on a placeholder directory and on a leaf, including a wrapped continuation, update the scenario output, and mention the column in the help.