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/psi/EnumCommas.txt

@@ -0,0 +1,37 @@
+JetFile: EnumCommas.kt
+  PACKAGE_DIRECTIVE
+    <empty list>
+  CLASS
+    MODIFIER_LIST
+      PsiElement(enum)('enum')
+    PsiWhiteSpace(' ')
+    PsiElement(class)('class')
+    PsiWhiteSpace(' ')
+    PsiElement(IDENTIFIER)('Color')
+    PsiWhiteSpace(' ')
+    CLASS_BODY
+      PsiElement(LBRACE)('{')
+      PsiWhiteSpace('\n    ')
+      ENUM_ENTRY
+        OBJECT_DECLARATION_NAME
+          PsiElement(IDENTIFIER)('NORTH')
+      PsiElement(COMMA)(',')
+      PsiWhiteSpace('\n    ')
+      ENUM_ENTRY
+        OBJECT_DECLARATION_NAME
+          PsiElement(IDENTIFIER)('SOUTH')
+      PsiElement(COMMA)(',')
+      PsiWhiteSpace('\n    ')
+      ENUM_ENTRY
+        OBJECT_DECLARATION_NAME
+          PsiElement(IDENTIFIER)('WEST')
+      PsiElement(COMMA)(',')
+      PsiWhiteSpace('\n    ')
+      ENUM_ENTRY
+        OBJECT_DECLARATION_NAME
+          PsiElement(IDENTIFIER)('EAST')
+      PsiElement(COMMA)(',')
+      PsiWhiteSpace('\n    ')
+      PsiElement(SEMICOLON)(';')
+      PsiWhiteSpace('\n')
+      PsiElement(RBRACE)('}')