Build process cleanup

TL;DR on changes:

* Clone of this repo followed by executing `.\make.cmd` (Windows) or `make` (Mono) will restore all necessary packages. Linux build will install Mono on OS X / Ubuntu if missing
* Merged a lot of the documentation files (`THANKS`, etc) into `README.md`
* Removed all extraneous binary files that were checked in (`packages` dir mostly). Ensure that Windows and Mono build processes restore packages when run.
* `build` directory has canonical Makefile/MSBuild files
* `riak_pb` repository added as submodule in `src/riak_pb`. Build target to regen `.cs` files from `.proto` files is in `build.proj` (`ProtoGen` target)
* Necessary executables for protobuf-net checked into `tools/protobuf-net`
* Script to set up devrel in `tools/setup-dev-cluster`
* Consolidated projects into `src/` directory
* Version and NuGet packaging targets in `build.proj`