* Send show_values key to static-viz js

The static viz components expect certain keys on the settings map passed into the js. At this time, the contract
between the backend (Clojure) and the static-viz (js) feels a little under-specified. However, for the change to XY
Charts here, we follow the existing method in code of checking the backend viz-settings map for some key, and passing
it into js in a 'simplified' form. For instance, in this change, `:graph.show-values` is taken and placed into the
settings map as `:show_values` for the static-viz js to use.

* De-dupe key

* Keep this PR super simple, don't eliminate sparkline stuff yet

* Add :line earlier in cond, try to fix tests that fail

* Get the :line conditional in the right place, allowing :scalar