Common lib: move hsieh hash into KFS namespace.
Meta server: first working / usable user and group implementation. Use smart pointers to pass and update user mapping to the client threads. Change handling of group and password "files" duplicate entries, only report errors if duplicate entries are different / conflicting, and skip such entries. Replace user name to id mapping in the client authentication context with the corresponding tables from user and group class tables. Obtain and set default user's group as effective group in the client state state machine and propagate / assign the group to all rpcs received by the client state machine instance. Implement name lookup using delegation uid. Declare authentication failure if user id lookup fails and the delegation token doesn't have chunk server bit set. Implement client threads authentication context update when user and group information changes, then update mechanism is similar to the client authentication context parameters update, except that it is more lightweight, as the update only requires smart  pointer manipulation (boost shared_ptr).