We've decided to include a JRE for Mac Greenstone binaries, since later versions of Macs (like Yosemite) do not come with Java. Adding the generated jre 1.7.0_79 self-extracting binary and its related p7z component. Jeremy had long ago compiled up the p7z-essentials binaries 7za and 7zCon.sfx on the Mac that are necessary for generating the Mac self-extracting jre binary.