Enable OpenCart Demo on Trafodion Downloads

Enable the OpenCart Demo to be downloaded from the Trafodion
Downloads site http://downloads.trafodion.org. The download
site has also been changed to a 2 column format to facilitate
this.

Change-Id: I07232c1e158d102d5f4ba71f122c8e8b41cf7103
Closes-Bug: 1357140
Merge "Enable OpenCart Demo on Trafodion Downloads"