Added RDB_SERIALIZE_OUTSIDE.
Moved directory_echo.tcc to directory_echo.cc.
Added RDB_SERIALIZE_TEMPLATED_OUTSIDE.
Made RDB_SERIALIZE_TEMPLATED_OUTSIDE be variadic.
Moved multi_throttling_server_business_card_t out of multi_throttling_business_card_t, likewise with client.
Used RDB_SERIALIZE_TEMPLATED_OUTSIDE for multi_throttling_metadata.hpp.
Used RDB_SERIALIZE_OUTSIDE in a lot of places.
Some more RDB_SERIALIZE_OUTSIDE lines (for manual rdb_serialize implementers).  Removed the generic serialize and deserialize helpers.