rename JESIntro to JESIntroduction like I was supposed to

I changed the filename of JESIntro.txt to JESIntroduction.txt in the
code when I was moving everything around, but I forgot to actually
rename the file. And since it only tries to open JESIntroduction.txt
on the first run, I didn't realize anything was wrong.
make working jes.bat for Windows

jes.bat is just a port of jes.sh to a batch file, which is much easier
than porting the Makefile to a batch file. It configures all the same
system properties and environment variables, and uses JAVA_HOME the same
way. (Though soon it will need to be modified to deal with vendored
JRE's.)