JengaDev v1.0.27

Fixes two related hosts-file bugs:

• Creating hosts across separate sessions added a brand-new "# Added by
  JengaDev" comment header every time instead of growing one list, so
  the Windows hosts file accumulated duplicate headers.
• If the Windows permission prompt needed to edit the hosts file was
  declined or missed, host creation silently reported success anyway,
  with no indication the new domain wouldn't actually resolve.

Both fixed. No other functional changes.