Fixed: Shows enabled text for both enabled and disabled message

- Added toggle command for toggle sprint acceleration
- Store related data in player metadata (speed level & toggle state)
- Refactored source code

- Ported to Gradle project
- Added world whitelist/blacklist (Config: world-list, world-list-type)
- Added permission based sprint acceleration (Config: sprint-permission)

- Messages rewrited to English language.
- Potion effect sometimes stucked -> Fixed
- Tested in 1.15.2, it works fine with that version too