[Add]return engine/gateway object when adding related class to MainEngine
[Add]return engine/gateway object when adding related class to MainEngine

msincenselee/vnpy,msincenselee/vnpy,msincenselee/vnpy,bigdig/vnpy,msincenselee/vnpy,andrewchenshx/vnpy,andrewchenshx/vnpy,bigdig/vnpy,andrewchenshx/vnpy,vnpy/vnpy,bigdig/vnpy,andrewchenshx/vnpy,andrewchenshx/vnpy,vnpy/vnpy,bigdig/vnpy