to having a default.properties define the properties and
allow people to define their own properties easily by creating
a build.properties file.
I also updated the documentation to clearly lay out what one needs
to do to define their own properties.
-jon
git-svn-id: https://svn.apache.org/repos/asf/lucene/java/trunk@149709 13f79535-47bb-0310-9956-ffa450edef68