2.1.0

• A new minor release to support Hierarchy Builder 1.8.
• Added automation for reasoning about uniqueness of sequences.
• Added a type class of conical PCMs.
• Made dom infer the union_map structure, in order to support structure-specific notation for dom.
• Added a type class of total map-like functions in unionmap.v. Previous version had only partial map-like function (omap_fun), but total ones admit better lemmas.
• Generalized several \big lemmas in unionmap.v that were previously unnecessarily restricted (bigD1FE, bigPtUnE, bigPtUn, bigDUE).
• Added a number of smaller lemmas in pred, prelude, seqext, unionmap.