Case insensitive file/directory name matching will produce errors on M/R jar unpack.

This only seems to affect platforms where there can be a file/directory naming conflicts
from case insensitive matches.

I was able to reproduce running the pseudo-distributed unit tests within OSX.

This has affected other projects:
https://issues.apache.org/jira/browse/MAHOUT-780

I've been able to reproduce this on my local OSX install with the following error:
https://groups.google.com/a/cloudera.org/group/cdh-user/browse_thread/thread/a201218000e956d3/cc6eca3ef9f80ff8

Since LICENSE.txt contains the same content as the file LICENSE, I propose we exclude any LICENSE matches found in the unpacked dependency jars
when the maven assembly phase hits 'jar-with-dependencies'.

I have a patch which moves the 'jar-with-dependencies' descriptor to an external compile.xml file which has the proper excludes. This might also
come in handy down the road should any additional tweaks be needed to the compile phase.