TODOs for the next release

[wangvsa]

Some of the tasks I need to work on:

1. Margo DTL: PUSH vs PULL? For now, I am using RDMA pull, but perhaps should switch to RDMA push to reduce one message.
2. Margo DTL: Runtime network layer (cxi, tcp, ucx, verbs) selection. It's hardcoded to TCP right now. We should support runtime selection.
3. Debug information should include client/service information (e.g., ranks, node id)
4. Margo-based service: KVS and RPC (do PRC first)
5. Implementing a monitoring service on the consumer directory so we can perform eviction actions.
6. Consider supporting UCX driver underneath Margo, then we can remove the UCX prat of implementation.