#202 override directory for settings and user data files

[Legion]

id like to have all files in one main dir (and subdirs)
no nothing writen to any other part of the computer
c:\openmsx\
c:\openmsx\settings\
c:\openmsx\bin\
and so on
with any files that would normally be writen on another part of the system would now be in the \settings\ dir (for example)
same goes for any othere files that dont come with the openmsx installer/zip

for updating you would only need to delete all but \settings\
and unpack the new zip

[Manuel Bilderbeek]

This is a duplicate of https://sourceforge.net/p/openmsx/feature-requests/224/ Using 224 now as main item.