[Feature] Burn Address

[yun-yeo]

NOTE:: THIS MUST BE MERGED AFTER #323

Summary of changes

On the EndBlocker, check burn account balance and burn all tokens in that account. Burn account is module account with burner permission (terra1sk06e3dyexuq4shw77y3dsv480xv42mq73anxu).

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 #343 into develop will decrease coverage by 1.04%.
The diff coverage is 50.00%.

@@             Coverage Diff             @@
##           develop     #343      +/-   ##
===========================================
- Coverage    69.50%   68.46%   -1.05%     
===========================================
  Files           70       72       +2     
  Lines         3558     3618      +60     
===========================================
+ Hits          2473     2477       +4     
- Misses         948     1004      +56     
  Partials       137      137              

Impacted Files	Coverage Δ
x/bank/module.go	0.00% <0.00%> (ø)
app/app.go	85.89% <100.00%> (ø)
x/bank/abci.go	100.00% <100.00%> (ø)