More consistent hover states for styles and components

[endigo9740]

Currently we use a mix of +/- 10% brightness for a lot of hover states (ex: Buttons, etc). The standard for most libraries is to increase brightness on hover state, so we'll aim for that to be our new default. Of course this can typically be overwritten and changed on a per-component basis using the props/TW styles. But consistent defaults would be nice!

[endigo9740]

These updates are now complete and ready for testing. The most notable change is to tabs. We didn't really have hover styles. The TW classes have been updated to allow for this. Likewise I've split the highlight prop into two dedicated props:

border - controls the highlighted element's border color
fill - controls the highlighted element's SVG icon color

These needed to be set on different elements so best to do it this way. Results are more consistent and work well in practice. Plus it open the door for two-tone icon/label highlights.