Brains Update - UI retouches

It's been about two years since I've released Brains, but there are still a few things I've wanted to tweak that have kept me up at night.
This update is mainly focused on re-spriting Brains' unique UI elements, with a focus on making them look cleaner and more inline with Nuclear Throne's artstyle.

Changes include:

- New look for the target symbol for targeted enemies - added empty notch sprites for the timer indicator
- The enemy selection reticule is marginally different
- New look for the Focus Meter - The moving bar now also properly goes under the meter's edges
- Focus Meter now appears under Brains in Multiplayer to avoid underlapping with the Player Number indicator

- Character Portraits slightly touched up (mainly regarding lines of shading/lighting)

I promise that whatever the next update will be, it will be the last. The only things left I want to add are unique voice clips and compatibility with 60fps. I'll probably also need to update the page itself to make it actually look halfway decent after all this time.

I also want to thank everyone who has given Brains a shot over the years! It really means a lot to me that people have been adding my little goober to their cast of Nuclear Throne characters!