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`. 
Consistency: here we call the curried constructor `plus` and in line 27 we call the plain constructor. I think we may want to stick with one.

P.S. It seems easiest to adopt the convention that calls curried constructor everywhere and rely on the compiler to optimize it away. (I remember reading about such optimization in either 4.01 or 4.02?)