DS-2302 Remove license headers from config files

https://jira.duraspace.org/browse/DS-2302

Files such as xmlui.xconf have a tremendous amount of comments, which is a giant license header, and then very verbose usage instructions. Just like there aren't instructions on a light switch (switch can be up or down, but not both up and down), some of this verbosity is too much. So, I've made a sweep through dspace/config, and removed license headers. The actual DSpace code needs license headers, but not these configs.