Feature/adopt gov module

[yun-yeo]

Summary of changes

As proposed #216 & #204 , add governance module. distribution module already contains community-pool-spend proposal suitable for budget so budget module is removed. There are two custom governance proposals from treasury module; tax-rate-update&reward-weight-update proposals.

New EndPoints

(GET)/gov/proposals
(GET)/gov/proposals/{proposalId}
(GET)/gov/proposals/{proposalId}/proposer
(GET)/gov/proposals/{proposalId}/deposits
(GET)/gov/proposals/{proposalId}/deposits/{depositor}
(GET/POST)/gov/proposals/{proposalId}/votes
(GET)/gov/proposals/{proposalId}/votes/{voter}
(GET)/gov/proposals/{proposalId}/tally
(GET)/gov/parameters/deposit
(GET)/gov/parameters/tallying
(GET)/gov/parameters/voting
(POST)/gov/proposals/tax_rate_update
((POST)/gov/proposals/reward_weight_update
(POST)/gov/proposals/param_change
(POST)/gov/proposals/community_pool_spend

Report of required housekeeping

• Github issue OR spec proposal link
• Wrote tests
• Updated relevant documentation (docs/)
• Added a relevant changelog entry: clog add [section] [stanza] [message]

---

(FOR ADMIN) Before merging

• Added appropriate labels to PR
• Squashed all commits, uses message "Merge pull request #XYZ: [title]" (coding standards)
• Confirm added tests are consistent with the intended behavior of changes
• Ensure all tests pass

[codecov]

Codecov Report

Merging #234 into develop will increase coverage by 0.26%.
The diff coverage is 73.33%.

@@             Coverage Diff             @@
##           develop     #234      +/-   ##
===========================================
+ Coverage    67.57%   67.83%   +0.26%     
===========================================
  Files           68       70       +2     
  Lines         2942     3050     +108     
===========================================
+ Hits          1988     2069      +81     
- Misses         846      872      +26     
- Partials       108      109       +1

[dokwon]

LGTM