docs/TODO: cleanup/re-organize. Add more languages.
C#: step0_repl using de Icaza's getline.cs
C: fix step1 EOF handling.
CS: add step1_read_print
C#: add step2_eval.
CS: add step3_env

Also, make Makefile more closely match the C Makefile.
CS: add step4_if_fn_do
C#: add step5_tco
C#: step6_file
C#: add step7_quote
C#: add step8_macros
C#: add stepA_more and core functions.
C#: add metadata and atoms.
README: add C# info. Cleanup top Makefile.

Also, re-order impls into alphabetical order.
Fix metadata on functions.

- Don't use metadata to store ast, env, params data.
- In Clojure, store metadata on the :meta key of the real metadata.
  This also allows using any datatype as metadata.
Add stats-lisp target (only env, core, stepA)
Ruby: step0, step1
Ruby: step2_eval
Ruby: add step3
Ruby: step4_if_fn_do with core functions.