Adds aesthetics for plot components used in this package.
Details
This package attempts to generate a consistent
theme even if users are working with a highly
customized xp_theme. There is are only a few
hard-coded aesthetics, and the rest are derived from
existing aesthetics in base_on, which defaults to
the default from xpose.
Only a few options are worth noting. In <xplot_pairs>
(and functions using it), the aesthetics for GGally-specific
elements like barDiag are defined as gga(element)_(aesthetic).
The labeller for pairs plots is also changed from the de facto default
label_both to label_value, but any labeller can be provided as
pairs_labeller.