Widely implemented list handler, removed unit wrapper, updated physchem

• The core.utility.list_handler() function decorator has been widely applied to functions in the research and core subpackages, allowing them to accept and output either scalar or array quantities.
• The u.wraps() unit wrapper, which was causing poor programming practice and many bugs, has been removed from the entire package.
• Documentation and naming of functions in core.physchem have been improved and standardized. Deprecation warnings have been included for functions and parameters that are changing names.