* Test coverage for Challenges Command
* Added CompleteChallengeCommand test class
* Added Utils test class
* Added ChallengesGUI test class
* Fix code smells from sonarcloud analysis
* Added .gitignore
* Added Travis CI config file
* WIP ChallengesManager Test class
* Added ChallengesManager test class
* Removed debug
* Removed code smells.
* Added ChallengesAddon test class.
* Added onDisbale test
* Added new TryToComplete test class - WIP
Covers inventory challenges.
* Added Island Challenge entity tests to TryToComplete test class
Rework methods that access to ChallengesPlayerData object. Methods that access to this object will be private and use UUID and String where possible.
Add public methods that could use previously mentioned methods to access ChallengesPlayerData object.
Implement these methods in all places.
Add ability to enable/disable island storage in config (no-gui for now).
Disable challenge GUI opening, if user does not have island.
Implement all methods that were only placeholders.
Remove all unnecessary old methods.
Implement new methods in all classes.
User and Admin command now opens new GUI.