Make options more consistent

Some options are available only through the decorator (e.g. the style), while some are accessible as command-line options and one (the results dir) is also an ini option. We should make this more consistent so that e.g. styles can be set globally on the command-line or in an ini file.

Start by inventorying how decorator, command-line, and ini options are defined and parsed, especially the style and results-directory options. Compare their configuration paths and determine the consistent behavior required; done means the relevant options are available through the intended interfaces with matching precedence and tests.

Written by the indexing model from the issue text.