Add BitcoinRpcNetworkProvider

[blockparty-sh]

This adds a new network for interacting directly with a bitcoin cash node over rpc. It is based on http://github.com/blockparty-sh/cashscript-regtest

[codecov-io]

Codecov Report

Merging #89 (0e49506) into master (907a5f8) will decrease coverage by 0.42%.
The diff coverage is 18.18%.

@@            Coverage Diff             @@
##           master      #89      +/-   ##
==========================================
- Coverage   95.02%   94.59%   -0.43%     
==========================================
  Files          36       37       +1     
  Lines        1969     1980      +11     
  Branches      257      257              
==========================================
+ Hits         1871     1873       +2     
- Misses         93      102       +9     
  Partials        5        5              

Impacted Files	Coverage Δ
.../cashscript/src/network/ElectrumNetworkProvider.ts	85.96% <ø> (ø)
...ashscript/src/network/BitcoinRpcNetworkProvider.ts	18.18% <18.18%> (ø)

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