info: show whether unimplemented exercises have canonical data (#567)
info: show whether unimplemented exercises have canonical data (#567)

Before this commit, the output of `configlet info` would not indicate
whether an unimplemented exercise has canonical data. For example, the
output might contain:

    There are 14 non-deprecated exercises in `exercism/problem-specifications` that
    are both unimplemented and not in the track config `exercises.foregone` array:
    dot-dsl
    error-handling
    hangman
    killer-sudoku-helper
    ledger
    lens-person
    markdown
    micro-blog
    paasio
    parallel-letter-frequency
    pov
    sgf-parsing
    state-of-tic-tac-toe
    tree-building

With this commit, we output two separate lists:

    There are 14 non-deprecated exercises in `exercism/problem-specifications` that
    are both unimplemented and not in the track config `exercises.foregone` array:
    
    With canonical data:
    killer-sudoku-helper
    markdown
    micro-blog
    pov
    sgf-parsing
    state-of-tic-tac-toe
    
    Without canonical data:
    dot-dsl
    error-handling
    hangman
    ledger
    lens-person
    paasio
    parallel-letter-frequency
    tree-building

This is useful because:

- It is often easier to implement an exercise that has canonical data.

- For a track that has previously implemented every exercise that has
  canonical data, it is now easier to see that no new exercise with
  canonical data has been added to problem-specifications.

Closes: #481

exercism/configlet