Fix rst markup for sage/combinat/sf/sf.py (and add to manual) and sage/structure/dynamic_class.py

[SimonKing]

In the two files named in the title, the .. topic:: directive is improperly used (namely as ..topic: without the blank space and with only one colon), and moreover it should actually be .. rubric:: instead.

Moreover, some lists are indented too much, and in some case an empty line is missing, such as

    Further things to do:
     - Use UniqueRepresentation to get rid of all the manual cache handling for the bases
     - Devise a mechanism so that pickling bases of symmetric functions pickles
       the coercions which have a cache.

versus

    Further things to do:

    - Use UniqueRepresentation to get rid of all the manual cache handling for the bases
    - Devise a mechanism so that pickling bases of symmetric functions pickles
      the coercions which have a cache.

In some places a double colon :: was missing.

I also suggest to use the .. todo:: markup more often.

And last but not least, I believe that sage/combinat/sf/sf.py should be put into the reference manual.

[SimonKing]

Ready for review.

[nthiery]

While we were at it, I did a couple minor changes around yours. Since the patch was short anyway, I allowed myself to refresh my review directly in it rather than writing a reviewer's patch. Please browse through, and if you are happy you can set a positive review on my behalf.

[SimonKing]

Your additions look fine to me!