kvstore test with cargo-make invoking docker

[greg-szabo]

The next step in #723.

• Introduces the tools folder. Currently only the new kvstore-test crate is in it, but we will add the docker folder, proto-compiler and rpc-probe crates too in time.
• The new kvstore-test crate uses cargo-make to make the integration tests from the tendermint crate and the tendermint-light-client crate first class citizens.

To execute the tests locally, enter the kvstore-test folder and run cargo test if you have a kvstore endpoint already running, or cargo make if you have the docker CLI installed but no endpoint running.

Benefits:

• Much smaller codebase

• The docker image shuts down automatically after a successful test run. (It still keeps running if tests fail, though.)

• Referenced an issue explaining the need for the change

• Updated all relevant documentation in docs

• Updated all code comments where relevant

• Wrote tests

• Updated CHANGELOG.md

[codecov-io]

Codecov Report

Merging #748 (e825a88) into master (27b3b73) will increase coverage by 0.9%.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           master    #748     +/-   ##
========================================
+ Coverage    42.1%   43.1%   +0.9%     
========================================
  Files         206     204      -2     
  Lines       13945   13620    -325     
  Branches     3571    3571             
========================================
- Hits         5876    5874      -2     
+ Misses       7695    7369    -326     
- Partials      374     377      +3     

Impacted Files	Coverage Δ
rpc/src/error.rs	44.4% <0.0%> (ø)
rpc/src/event.rs	11.1% <0.0%> (ø)
rpc/src/client.rs	9.3% <0.0%> (+2.1%)	⬆️
rpc/src/endpoint/abci_query.rs	28.5% <0.0%> (+6.3%)	⬆️

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[thanethomson]

Excellent! I tested this out locally and it works great, thanks Greg! 👍