PdfCraft portable mode

While this file sits next to pdfcraft.exe, PdfCraft keeps its settings, log files, crash-recovery
autosaves and new digital IDs in the PdfCraftData folder beside it, and writes nothing to
%APPDATA% or %LOCALAPPDATA%. Copy the whole folder to move PdfCraft with its settings.

Delete this file to use the normal per-user folders (%APPDATA%\PdfCraft and
%LOCALAPPDATA%\PdfCraft) instead. If PdfCraftData can't be written (for example on a read-only
drive), PdfCraft says so and uses the per-user folders instead.