KT-2625 Parse multiple assignment to variables

New PSI element types introduced.
Parsing procedure for properties reused.
Extra syntactic elements (receiver, type) are prohibited in the parser

#KT-2625 Fixed

grammar/src/class_members.grm

@@ -84,11 +84,12 @@ functionBody
 property
   : modifiers ("val" | "var")
       typeParameters? (type "." | annotations)?
-      SimpleName (":" type)?
+      (SimpleName (":" type)?){","}
       typeConstraints
       ("=" expression SEMI?)?
       (getter? setter? | setter? getter?) SEMI?
   ;
+
 /**
 bq. See [Properties and Fields]
 */