Added documentation todo

doc/doc/documentation_todo.txt

+
+==================
+Documentation todo
+==================
+
+    * Remove all links to wiki.
+    * Remove redundant text, e.g. index.txt, doc/index.txt, and doc/README.txt.
+    * Better organization, e.g. copy structure from trac wiki.
+        * Don't have a separate subdirectory doc/
+    * Reference the glossary terms more
+    * Don't use hard links
+    * Convert this? http://lgcm.iro.umontreal.ca/theano/wiki/CompileFunction
+    * Find all remaining trac wiki pages and convert them to sphinx
+    * Don't bury sphinx docs, make the sphinx docs the homepage and trac
+      accessible from within sphinx.
+    * Better integration of epydoc API and sphinx docs