Cleanup sharding library dependencies

Sharding components include a lot of libraries because the files are scattered around. This ticket is to do a first pass cleanup to help with the caching changes needed for SERVER-20854.

In particular:

• There should be no dependency on mongoscore other than mongos
• There is no reason for the sharding unit-tests to use the egress metadata hooks
• ChunkManagerTargeter is only used by the sharded write commands implementation so it should go under there
• The haveLocalShardingInfo initializer is only used on mongod, so it should be there only.