Make population compression platform independent

[kephale]

Should be an easy tweak, but I ran out of time. Change:

if( new java.io.File( "popcompressor.sh" ).exists() && !( System.getProperty("os.name").toLowerCase().indexOf("win") >= 0 ) )// need script + not windows
Runtime.getRuntime().exec("./popcompressor.sh "+folderName+" population_"+currentGen);

to something that will use either an archiving library or java's built in zip functionality.