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.

[codecov[bot]]

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 :warning:
src/external/bitcoin.rs	0.00%	27 Missing :warning:
src/blockchain/block.rs	0.00%	21 Missing :warning:
src/bill/mod.rs	0.00%	14 Missing :warning:
src/web/handlers/bill.rs	0.00%	13 Missing :warning:
src/blockchain/chain.rs	0.00%	12 Missing :warning:
src/util/rsa.rs	0.00%	2 Missing :warning:
src/dht/event_loop.rs	0.00%	1 Missing :warning:
src/external/mint.rs	0.00%	1 Missing :warning:
src/external/time.rs	0.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ 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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