packaging: Refactored Makefile and cpp Cmake file.

Now the two required thirdparty libraries Google protobuf and googletest are built by the Makefile (see target client_thirdparty) and only rebuilt if their source has changed (no longer waiting for configure to complete at every make client :-).

I also cleaned up the Cmake file and removed a lot of unnecessary include_directories. In consequence, a line in json-forwards.h had to be commented out.

git-svn-id: https://xtreemfs.googlecode.com/svn/trunk@2522 f8528748-c2c0-11dd-ba5c-d3b7c2b3b534