Project cleanup

[TacoTheDank]

• Delete unused/generated files
• Update gradle wrapper to 6.4.1 using git bash
• Separate dependencies into groups
• Update buildTools 28.0.3 -> 29.0.3
• A tiny bit of code cleanup
• Update Google Play badge link

[TacoTheDank]

@yellowbluesky It was made automatically when Git Bash updated the gradle wrapper.

[TacoTheDank]

No changes made to the one specific usage of commons:io between 2.6 and 2.7, so that's good.