Verify prebuild scripts for UE versions below 4.17#7

I'm not certain all the PreBuildSteps features this uses were supported in the past. It would be good to know for certain whether there are versions that can't be supported. I'm fairly confident 4.15-4.10 work, though I haven't tested all of them yet. I'm incapable of testing 4.9 and lower without a VS2013 install, which is hard to find official downloads for. I was able to get an ISO from [here](http://go.microsoft.com/fwlink/?LinkId=393220) though I was unable to install it due to some kind of conflict in my dev environment. I'm incapable of testing 4.11 and lower without a pre-Update3 install of VS2015, which is no longer available as far as I can tell. I was able to get an ISO from [here](https://download.microsoft.com/download/b/e/d/bedddfc4-55f4-4748-90a8-ffe38a40e89f/vs2015.3.com_enu.iso) but it includes Update3 which is broken on 4.11 and lower. I'm guessing 4.8 and lower will have the most problems. It's possible PreBuildSteps aren't as fully featured. Verification Checklist: - [x] 4.16 - [x] 4.15 - [x] 4.14 - [x] 4.13 - [x] 4.12 - [ ] 4.11 - [ ] 4.10 - [ ] 4.9 - [ ] 4.8 - [ ] 4.7 - [ ] 4.6 - [ ] 4.5 - [ ] 4.4 - [ ] 4.3 - [ ] 4.2 - [ ] 4.1 - [ ] 4.0