Clean up includes of authorization headers

Conflicts:
	src/mongo/db/commands.cpp
	src/mongo/db/commands/cpuprofile.cpp
	src/mongo/db/compact.cpp
	src/mongo/db/dbcommands_admin.cpp
	src/mongo/db/driverHelpers.cpp
	src/mongo/db/index.cpp
Rename AuthExternalState to AuthSessionExternalState

Conflicts:
	src/mongo/db/auth/SConscript
	src/mongo/db/auth/auth_session_external_state.cpp
	src/mongo/db/auth/auth_session_external_state_d.cpp
	src/mongo/db/auth/auth_session_external_state_s.cpp
SERVER-9518 Initial implementation of new User class
SERVER-9518 Small change to comment
Rename PrincipalName to UserName

Conflicts:
	src/mongo/client/sasl_client_authenticate_impl.cpp
	src/mongo/db/auth/authorization_session_test.cpp
	src/mongo/db/auth/user_name.h
	src/mongo/db/dbwebserver.cpp
	src/mongo/shell/dbshell.cpp
Add AuthGlobalExternalState
Set up a single global AuthorizationManager in mongos and mongod

Conflicts:
	src/mongo/db/auth/authorization_manager.h
	src/mongo/db/db.cpp
	src/mongo/s/server.cpp
Fix assert code
Rename Auth[Global,Session]ExternalState

Conflicts:
	src/mongo/db/auth/authz_session_external_state_d.cpp
	src/mongo/db/auth/authz_session_external_state_s.cpp
	src/mongo/db/db.cpp