create the edu.rice.cs.drjava.md5 properties file/resource bundle
containing the MD5 checksums of all files in the drjava.jar file.
Currently not used automatically when running "ant jar" since the
md5.properties file is already 0.5 MB in size. I will go back to the
approach of storing the MD5 checksums in the drjava.jar if it turns
out that generating them fresh every time is a time bottleneck.
AM src/edu/rice/cs/util/MD5ChecksumProperties.java
M build.xml
