Ability to display RNA duplexes

[tfenne]

Please let me know if there's a better avenue for discussion than opening an issue.

It would be really nice if Forna could support RNA duplexes in the form that various Vienna programs do (i.e. concatenated with &s between them). Minimally it would be helpful if Forna's input parser would detect the duplex format and either strip out the &s or replace them with some other symbols that Forna accepts.

Better would be to have some support for displaying the two sequences separately - e.g. restarting the base numbering at the transition between sequences, and then making the two sequence visually distinct (different colors for the text within the base bubbles? different borders?, etc.).

Forna generates by far the nicest visualizations of any RNA structure viewer I've found, but generating clear structures for duplexes isn't really possible.