Stellar meter and gradual fillbars added

- The player's stellar drive meters have finally been added!
- Health and stellar meters now increase or decrease their fills
gradually instead of being drawn to their exact sizes per frame.

To do:
- Color the health and stellar fillbars a bit so they stand out/look
nicer
- The stellar meters are currently using placeholder values as Chico
hasn't implemented this in-engine yet.
- Start using art assets (this will most likely have to wait until after
the capstone deadline and presentation)
UI assets added to project

Wasn't able to place these in the last commit due to running into issues
with the GitHub GUI.