Move away from dictionaries to initialise DataObjectMixin classes

**Is your feature request related to a problem? Please describe.**
Entering a dict isn't intuitive and should be entered by named parameters instead. We should keep initialisation by dict as a "from_dict" classmethod.

**Describe the solution you'd like**
Remove the dict from the DataObjectMixin init. Update all derived classes to have a named parameter for all possible keywords in the keyword mapping dicts.

Start by locating DataObjectMixin, its derived classes, and the keyword mapping dictionaries. Trace how those classes are currently initialized and identify the existing dictionary conversion path. Done means derived classes accept named parameters, dictionary initialization is provided through a from_dict classmethod, and all affected mappings are updated.

Written by the indexing model from the issue text.