JAL-4354 First cut at allowing superimposition of structures. Use...
requested to merge improvement/JAL-4354_allow_many_structures_to_be_loaded_and_viewed_via_command_line into develop
JAL-4354 Allow multiple structures in one structureviewer from the command line with or without superposition.
See https://issues.jalview.org/browse/JAL-4354?focusedCommentId=28241&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-28241 for some example test commands.