Keep development doc sync with latest code

[penghuo]

*Issue #, if available: N/A

*Description of changes: Update the Developer Guide

1. Add the Elasticsearch OSS and Kibana OSS download link. Currently, it to official Elasticsearch website because ODFE Kibana doesn't have MAC version.
2. Fix the integ-test command.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov]

Codecov Report

Merging #961 (dc2f9a1) into develop (0855c53) will increase coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             develop     #961   +/-   ##
==========================================
  Coverage      99.87%   99.87%           
- Complexity      2341     2347    +6     
==========================================
  Files            232      232           
  Lines           5389     5395    +6     
  Branches         350      350           
==========================================
+ Hits            5382     5388    +6     
  Misses             5        5           
  Partials           2        2           

Impacted Files	Coverage Δ	Complexity Δ
...roforelasticsearch/sql/sql/parser/ParserUtils.java	100.00% <0.00%> (ø)	7.00% <0.00%> (+6.00%)
...ticsearch/sql/sql/parser/AstExpressionBuilder.java	100.00% <0.00%> (ø)	48.00% <0.00%> (-2.00%)
...csearch/sql/analysis/WindowExpressionAnalyzer.java	100.00% <0.00%> (ø)	12.00% <0.00%> (+2.00%)
...rch/sql/sql/parser/context/QuerySpecification.java	100.00% <0.00%> (ø)	15.00% <0.00%> (ø%)

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