ant's portable DOSBox installation

DOC -- DOSBox documentation
BOX -- DOSBox binaries
CFG -- DOSBox configuration files
RUN -- per-program entries
DOS -- disc C: of the emulated MS-DOS system

To add a game:
1. Put the game's binaries under DOS\
2. Create a batch file in RUN\ for running that game.

A per-program entry is a .bat file that serves both for
launching DOSBox and for supplying program-specific settings.
The first line shall always run the special entry with default
settings and optionally number of additional configuration
files,

   ..\BOX\init [config...] %~f0

The following text shall specify the desired DOSBox
configuration for the program, selectively overriding the
default configuration.  Since the entry files use rely on paths,
they must always be invoked with the working directory set to
their location.