Fixes Checkstyle Issues Related to DateTimeParsingTests

Revert Last Change in build.gradle

Upgrades JavaFX to 11

Encountering issue with Linux system not being able to be run with Djdk.gtk.version=2. Hopefully, this fixes it. I'll have to see when I deploy to Linux Ubuntu.

Fix an Issue with Linux systems Not Loading Background

The last version had the background in a jpg format, which for some reason is not able to be loaded properly on Linux based system. This version converts the image to PNG format.

Update README.md