Improve tests: Add pretty_org fixtures to allow testing pretty printing

Until now we expected the .org file to print back to itself - we can't do that
when the input is not pretty printed already - with the introduction of blocks
with unindented content that will be the case.

org/testdata/blocks.pretty_org

@@ -0,0 +1,50 @@
+#+CAPTION: block caption
+#+BEGIN_SRC bash :results raw
+echo "a bash source block"
+
+function hello {
+    echo Hello World!
+}
+
+hello
+#+END_SRC
+
+#+BEGIN_SRC
+a source block without a language
+#+END_SRC
+
+#+BEGIN_EXAMPLE foo bar baz
+an example block with
+multiple lines including
+
+
+empty lines!
+
+it also has multiple parameters
+
+note that /inline/ *markup* ignored
+#+END_EXAMPLE
+
+: examples like this
+: are also supported
+: note that /inline/ *markup* ignored
+
+#+BEGIN_QUOTE
+Mongodb is *webscale*. (source: [[http://www.mongodb-is-web-scale.com/][mongodb-is-web-scale]])
+
+blocks can contain other elements like
+- lists
+- inline /markup/
+- tables
+  | foo |
+  | bar |
+  | baz |
+- paragraphs
+- ...
+#+END_QUOTE
+
+#+BEGIN_EXPORT html
+<script>
+console.log("Hello World!")
+</script>
+#+END_EXPORT