Kepler

From an email from matt on kepler-dev:

I agree, it would be better if we could build without requiring that
JAVA_HOME is set. For that matter, I would prefer if we didn't need to
set KEPLER or PTII either. For KEPLER, we can use the ant basedir
property which is always set to the directory where the build is
launched -- this would be a simple change. Its not even clear to me
that env.KEPLER is used anywhere except in the javadoc target, and it
would be easily replaced with either a relative path or ${basedir}.

For PTII, I think we should check if PTII is set, and if so, check it
and use that dir, but if not then see if ptii is found in a sibling dir
of $KEPLER, and if so use that. If both of those fail, then abort with
an error saying we can't find ptii. By checking for the environment
variable first, we allow people to use different versions of PTII while
still making the default case where it is checked out in a sibling
directory the default.

These changes would significantly simplify our build and eliminate the
most frequently reported build problem that is reported to us.

Matt