Element v1.5.1 update. — Element Steam update #946201

Our labs have torn down and rebuilt a bunch of junk and Element v1.5.1 'Pulsar' is available now. Nearly all of the changes are under the hood, with some big refactorings of our plumbing and difficulty systems to prepare for future v1.6 updates. On the surface everything should play the same so please let us know if anything is misbehaving. We have also updated the Steam, input, sound, and JSON libraries which should be seamless. There are a couple of shiny bits amongst the mundane library update waffle, including a small unit spawn animation, some updated explosion effects, and a new epilogue animation. This update also removes the Linux rendering workaround we had in place to fix some camera compositing issues. We had reports that v1.5 was working as expected in full quality mode, so this update restores full quality by default. Remember to check out the full v1.5 updates from a few we...