fixes and readme

[turuslan]

• simplify readme, split docs/miner.md and docs/devnet.md.
• fuhon-node and fuhon-miner install targets.
• update libp2p, fix gtest.
• docker example.
• fix --help flag.
• add --api-ip flag for docker.
• rename --import-snapshot to --use-snapshot, user friendly error.
• default drand options.
• add actors v6 to compacter.

To preview new readme - https://github.com/filecoin-project/cpp-filecoin/blob/fixes-readme/README.md.

[codecov[bot]]

Codecov Report

Merging #528 (56955fe) into master (8c7c60e) will decrease coverage by 0.05%. The diff coverage is 9.09%.

@@            Coverage Diff             @@
##           master     #528      +/-   ##
==========================================
- Coverage   46.49%   46.43%   -0.06%     
==========================================
  Files         676      676              
  Lines       29950    29980      +30     
  Branches    16591    16609      +18     
==========================================
- Hits        13924    13920       -4     
- Misses      11999    12030      +31     
- Partials     4027     4030       +3     

Impacted Files	Coverage Δ
core/miner/main/main.cpp	0.00% <0.00%> (ø)
core/node/main/builder.cpp	1.55% <0.00%> (ø)
core/node/main/config.cpp	0.00% <0.00%> (ø)
core/node/main/main.cpp	0.00% <0.00%> (ø)
core/storage/compacter/lookback.hpp	68.18% <50.00%> (-5.16%)	:arrow_down:
core/crypto/blake2/blake2b160.cpp	88.00% <0.00%> (-1.34%)	:arrow_down:

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