160 fix all warnings during the build

[zupzup]

This implements #160 and fixes all warnings and clippy warnings.

The changes were all done in a way so there is no logic change.

[mtbitcr]

All good, only 3 minor comments

[codecov]

Codecov Report

Attention: Patch coverage is 9.48905% with 124 lines in your changes missing coverage. Please review.

Project coverage is 4.04%. Comparing base (072752c) to head (f1d31e6).
Report is 7 commits behind head on master.

Files with missing lines	Patch %	Lines
src/dht/client.rs	0.00%	32 Missing ⚠️
src/external/bitcoin.rs	0.00%	27 Missing ⚠️
src/blockchain/block.rs	0.00%	21 Missing ⚠️
src/bill/mod.rs	0.00%	14 Missing ⚠️
src/web/handlers/bill.rs	0.00%	13 Missing ⚠️
src/blockchain/chain.rs	0.00%	12 Missing ⚠️
src/util/rsa.rs	0.00%	2 Missing ⚠️
src/dht/event_loop.rs	0.00%	1 Missing ⚠️
src/external/mint.rs	0.00%	1 Missing ⚠️
src/external/time.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##           master    #188      +/-   ##
=========================================
- Coverage    4.19%   4.04%   -0.15%     
=========================================
  Files          29      29              
  Lines        7175    6871     -304     
=========================================
- Hits          301     278      -23     
+ Misses       6874    6593     -281     

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