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.

compiler/testData/diagnostics/tests/enum/enumMissingName.kt

@@ -0,0 +1,6 @@
+// Error: name should present
+enum class<!SYNTAX!><!>(val rgb : Int) {
+    RED(0xFF000),
+    GREEN(0x00FF00),
+    BLUE(0x0000FF)
+}