Island World Challenges

** 1.6 **
* 1.13 support
* Added support for challenge signs back

** 1.5 **
* 1.12.2 support

** 1.4 **
* Fixed logic while loading xml files

** 1.3 **
* Fixed problem with GUI inventory usage

** 1.2 **
* Logic fix in code fixing problem with wrong check for required items.

** 1.1 **
* If challenge doesn't have icon set, first reward icon will be used.

** 1.0 **
* Initial release