Extend {foo} syntax to allow {"foo"} as well.

Useful when "foo" contains unusual characters. Should help with
the issues #7, #38, #40, #42.

testdata

@@ -64,6 +64,10 @@ null
 {"a":1, "b":2, "c":3, "d":"c"}
 {"a":1, "b":2, "c":1, "e":2}
 
+{"a",b,"a$\(1+1)"}
+{"a":1, "b":2, "c":3, "a$2":4}
+{"a":1, "b":2, "a$2":4}
+
 #
 # Field access, piping
 #