updated internal docs

doc/internal/extending.txt

-.. _extending:
-
-================
-Extending theano
-================
-
-
-How to Add Transformations
-==========================
-
-WRITEME
-
-How to Create a Linker
-======================
-
-WRITEME
-
-How to Create a Transformation Mode
-===================================
-
-WRITEME

doc/internal/index.txt

@@ -13,5 +13,4 @@ Structure
 
    dev_start_guide
    hg_primer
-   extending
-   misc
+   metadocumentation

doc/internal/misc.txt → doc/internal/metadocumentation.txt

-.. _misc:
+.. _metadocumentation:
 
-================
-Miscellaneous
-================
+==================================================
+Documentation Documentation AKA Meta-Documentation
+==================================================
 
 
 How to link from Sphinx to API documentation
@@ -106,4 +106,4 @@ TO WRITE
  * How epydoc and sphinx are integrated
  * The nightly build process.
  * Explain the special magic in ./scripts/docgen.py
- * We also want examples of good documentaiton, to show people how to write sphinx,
+ * We also want examples of good documentation, to show people how to write sphinx,