Skript 2.6 / MC 1.17 support

Fixes:

• Fix the run section effect not storing a result
• Fix #34
• Fix #37
• Fix the event expression not returning the right event
• Fix events not being marked as delayed at runtime
• Make skript-reflect compatible with Skript 2.6
• Fix #39
• Make compiling output jar always Java 8 compatible
• Fix Java call descriptor parsing
• Change some warning prefixes
• Improve Java call errors
• Improve Java 16 compatibility

Additions:

• Added a class reference expression: https://tpgamesnl.gitbook.io/skript-reflect/basics/utilities#class-reference
• Added a simple warning if an import has an alias that's not needed