remove old and not working build.bat

Win32 will be eventually supported by the build.py script. This one is
obsolete.
Remove most of UNIX command references

Replaced most of UNIX command references with native Python equivalents
to make script more platform-independent. Added preliminary support for
Windows (you could build it by executing build.py with --force
parameter).
Fix for --force parameter in build.py

Sorry, I forgot about it.