Move DHT to dht/dht.py, update DHT figure

[justheuristic]

This is a chore PR, it does not change any functionality

• moved DHT to a separate sub-class [REFACTOR] general codebase updates for v0.10 #275
• updated DHT scheme (new paths, endpoint->peerID, 20bit -> 20byte)
• checked that benchmarks/exampels still work

[codecov]

Codecov Report

Merging #399 (7a3d295) into master (a09df54) will increase coverage by 0.38%.
The diff coverage is 90.06%.

@@            Coverage Diff             @@
##           master     #399      +/-   ##
==========================================
+ Coverage   83.36%   83.75%   +0.38%     
==========================================
  Files          72       73       +1     
  Lines        6673     6678       +5     
==========================================
+ Hits         5563     5593      +30     
+ Misses       1110     1085      -25     

Impacted Files	Coverage Δ
hivemind/dht/dht.py	89.87% <89.87%> (ø)
hivemind/dht/__init__.py	100.00% <100.00%> (+10.19%)	⬆️
hivemind/dht/routing.py	94.11% <100.00%> (ø)
hivemind/dht/node.py	91.44% <0.00%> (+0.71%)	⬆️
hivemind/averaging/matchmaking.py	84.49% <0.00%> (+6.68%)	⬆️