Make projects build into relevant subdirectories

Rather than dumping everything into a platform subdirectory in bin/, we
now build everything by default into a bin/.../intermediate
directory, except for top level executables (singlenode, clusternode,
testclient) etc which will include all the DLLs necessary for those
executables to run.

This will make scripting an ilmerge for the dependencies much simpler in
the future.
Merge pull request #151 from EventStore/build-reorg

Make projects build into relevant subdirectories