Update tooltip styling to better match game

[SaltedLevity]

Two key updates to do post live:

1. Add the clear "cap" to action icons to give them the rounder/matching display
2. update background to match textured game tooltip background, UI file is: https://cdn.discordapp.com/attachments/713141912848171110/713142275487825931/windowf_bgnormal_corner.tex.png test jsfiddle is: https://jsfiddle.net/g8bv6syL/ -- will need to specify fallback for crappy IE users.

[SaltedLevity]

Updating this as the clear cap has been added per #26 and refined later in #36

Updating background to have the textured background is extremely low priority and may be abandonded depending on accessibility issues.

Leaving this open until I make a decision, but it's extremely low priority.