Allow exporting to full paths

[VbScrub]

Fixes #76 and fixes #63

Tested with asktgt and the following paths as the /outfile argument and all works as it should:

C:\test\ticket.txt
\ticket.txt
C:\invalid/chars*.txt - file gets written to C:\invalid_chars_.txt
invalid/chars*.txt - file gets written to invalid_chars_.txt in working directory

For the record I still think we should ditch the whole file name sanitization thing, especially as it is not used universally throughout the program (kerberoasting for example does not sanitize file names, so that already let you use full paths for /outfile).

New PR as I messed up the old one

[VbScrub]

Hopefully this PR won't get affected by other changes I make in my own fork