Merged bap_types into bap_core

This version is essentially slightly modified `bap_types` from gerrit's master branch. The main difference is that is not a packaged library now, and that top library moved to `bap_core`.  Also, I've changed `README.md` file and added some handy tools, namely `baptop` and `bapbuild`. 
I want to correct my past: we should name this `mem_ref` to follow OCaml's underscore_in_compound_identifier convention.

Also, space.