add a deps check command

[Stebalien]

Checks for:

• Duplicate imports. Unlike gx deps dupes, the user won't need to follow up with a call to gx deps --tree --highlight=....
• Package version mismatch (version in dep list doesn't match version in package).
• Package name mismatch (name in dep list doesn't match name in package).

It also exits with an exit status of 1 if something needs to be fixed so we can run it from CI.

• [ ] Question: Currently, nothing in the output makes it clear that the package names listed under the duplicate import warnings are the parents that import that package. I could append "imported by" to the "$version $hash" line but that looks a bit funny...

Running this on go-ipfs right now prints out:

package protobuf imported as:
  - 0.0.0 QmT6n4mspWYEya864BhCUJEgyxiRfmiSY9ruQwTUNpRKaM
    - client_golang
    - client_model
    - common
    - golang_protobuf_extensions
    - go-ipfs
  - 0.0.0 QmXSs8cccbT4zDR95c1iRpYKDqVMzqeF1J6iZcavgE6eNw
    - badger
package go-detect-race imported as:
  - 0.0.0 QmQHGMVmrsgmqUG8ih3puNXUJneSpi13dkcZpzLKkskUkH
    - go-libp2p
  - 1.0.1 Qmf7HqcW7LtCi1W8y2bdx2eJpze74jkbKqpByxgXikdbLF
    - go-ipfs
package sys imported as:
  - 0.1.0 QmPXvegq26x982cQjSfbTvSzZXn7GiaMwhhVPHkeTEhrPT
    - go-sockaddr
    - go-reuseport
    - go-ipfs-cmdkit
    - badger
    - go-ipfs
    - go4-lock
  - 0.1.0 QmTq8ag5pgTCqtGDtmpm1F5TPE2i1H8bcU6295WFKTc5ie
    - fuse
  - 0.0.1 QmTsTrxKNXu8sZLv7FP6p884CHoDbT9upKA1j4FkCy5V7T
    - fsnotify.v1
package go-log imported as:
  - 1.4.0 QmRb5jh8z2E8hMGN2tkvs1yHynUanqnZ3UeKwgN1i9P1F8
    - go-ipfs
    - go-libp2p-secio
    - go-libp2p-peer
    - go-libp2p-peerstore
    - go-libp2p
    - go-libp2p-transport
    - go-libp2p-loggables
    - go-tcp-transport
    - go-addr-util
    - go-testutil
    - go-libp2p-conn
    - go-libp2p-swarm
    - go-libp2p-nat
    - go-libp2p-netutil
    - go-libp2p-blankhost
    - go-libp2p-circuit
    - go-multiplex
    - go-ds-flatfs
    - go-metrics-prometheus
    - go-libp2p-kad-dht
    - go-libp2p-record
    - go-libp2p-kbucket
    - go-libp2p-floodsub
    - go-ipfs-cmds
    - go-libp2p-connmgr
    - go-ipfs-addr
    - go-ipfs-chunker
    - go-ipfs-blockstore
    - go-fs-lock
  - 1.2.0 QmSpJByNKFX1sCsHBEp3R73FL4NF6FnQTEGyNAXHm2GS52
    - go-reuseport
dependency go-ipfs-cmdkit has version 1.0.0-dev but the referenced package has version 1.0.0