* Reduce Nim 1.6 compiler warnings/hints for Fluffy and Nimbus proxy
Mostly raises Defect removals, TaintedString removal and some
unnecessary imports.
Also updating the copyright years alongside.
* Further reduce Nim 1.6 compiler warnings/hints for Nimbus
* Improvements to the propagation and seeding of data
- Use a lookup for nodes selection in neighborhoodGossip
- Rework populate db code and add `propagateBlockHistoryDb` call
and portal_history__propagateBlock json-rpc call
- Small adjustment to blockwalk
* Avoid storing out-of-range data in the propagate db calls
Currently re-using http connections for the json-rpc requests
seems to slow down the requests considerably. Avoid this by
forcing a close after each requests in the blockwalk tool.
Kim De Mey