- Removes old paper_from_ref from repo. - Changes papers_from_citekey to get_paper. - Switches texnote plugin to new ref argument helpers.
- Moves shared command code to helpers module. - Implements reference(s) argument for commands: + a helper to add single or multi-reference argument to parser, + two functions to transform this argument into a list of citekeys.
TODO add papers dir to config on papers init command.
