New enum syntax: Short constructor syntax introduced for entries, optional commas between entries, semicolon after entries. #KT-7605 Fixed.

Grammar changed accordingly.
Semicolons prohibited after an entry except the last one.
Only one initializer is allowed per entry.
EnumReferenceExpression AST node introduced.
Some tests fixed, a pair of new tests written. Kotlin code inside project fixed.
Formatter and intendation tests fixed accordingly.
Stub version is incremented.

grammar/src/enum.grm

@@ -12,6 +12,11 @@ enumEntries
   : enumEntry*
   ;
 
-enumEntry
-  : modifiers SimpleName (":" initializer{","})? classBody?
+enumEntries
+  : (enumEntry ","? )?
+  ;
+
+
+enumEntry
+  : modifiers SimpleName ((":" initializer) | ("(" arguments ")"))? classBody?
   ;