[SETUPLIB][USETUP] Bring some suggestions from PR #59 in.

[SETUPLIB][USETUP] Bring some suggestions from PR #59 in.

- Use OBJ_CASE_INSENSITIVE when initializing object attributes
  (no actual reason why to keep case sensitivity there).

- Check the success of a RtlStringCchPrintfW call in EnumerateReactOSEntries().

- Explicitly check for returned STATUS_NOT_SUPPORTED from ChkdskPartition()
  or FormatPartition(), and display an appropriate error message.

- Remove some left-over comments but also explain why I kept some
  commented code (mainly for future reference).