Implement result blocks

org/testdata/blocks.pretty_org

@@ -1,3 +1,6 @@
+#+RESULTS:
+: some results without a block
+
 #+CAPTION: block caption
 #+BEGIN_SRC bash :results raw
 echo "a bash source block"
@@ -13,6 +16,14 @@ hello
 a source block without a language
 #+END_SRC
 
+
+#+BEGIN_SRC bash
+echo a source block with results
+#+END_SRC
+
+#+RESULTS:
+: a source block with results
+
 #+BEGIN_EXAMPLE foo bar baz
 an example block with
 multiple lines including