Rename config_archive.xml, archive_base.py, etc. to reflect their more general purpose

`config_archive.xml` and the associated python code have grown to be about more than just archiving. These are important, for example, in determining the history files that are examined by the test system (by defining history file suffixes). Thus, it seems that they should have more general names: keeping them named 'config_archive.xml', etc., gives the impression that these are only important if you care about archiving.

I'd suggest that these be renamed to something more general, like 'config_model_output.xml' and similar renames for the python. @rljacob also suggested this in https://github.com/ESMCI/cime/pull/2728#issuecomment-407579099 . He suggested `config_filenames.xml`, which I like. Note, though, that we already have a `config_files`, so we should be sure to pick a name that is distinct from that.