Add test cases for Proxy and fix some bugs

[tristaZero]

Fixes #601 .

Changes proposed in this pull request:

• Add test cases for Proxy
• modify ShardingDataSourceMetaData to final and change some test cases.
• Add more check items for orchestration to load
• Add default dataSource for show creat table merge result.

[codecov-io]

Codecov Report

Merging #1081 into dev will increase coverage by 1.1%.
The diff coverage is 32.6%.

@@            Coverage Diff            @@
##              dev    #1081     +/-   ##
=========================================
+ Coverage   56.02%   57.12%   +1.1%     
=========================================
  Files         636      636             
  Lines       12564    12572      +8     
  Branches     2014     2021      +7     
=========================================
+ Hits         7039     7182    +143     
+ Misses       5080     4938    -142     
- Partials      445      452      +7

Impacted Files	Coverage Δ
...etadata/datasource/ShardingDataSourceMetaData.java	100% <ø> (ø)	⬆️
...c/main/java/io/shardingsphere/proxy/Bootstrap.java	0% <0%> (ø)	⬆️
...e/metadata/table/executor/TableMetaDataLoader.java	0% <0%> (ø)	⬆️
...stration/internal/config/ConfigurationService.java	30.76% <0%> (-2.18%)	⬇️
...e/routing/type/standard/StandardRoutingEngine.java	0% <0%> (ø)	⬆️
...ng/type/broadcast/TableBroadcastRoutingEngine.java	89.47% <100%> (ø)	⬆️
.../core/jdbc/core/connection/ShardingConnection.java	82.75% <100%> (ø)	⬆️
...java/io/shardingsphere/core/rule/ShardingRule.java	83.82% <55.55%> (-2.34%)	⬇️
...e/merger/dal/show/ShowCreateTableMergedResult.java	93.75% <80%> (-0.19%)	⬇️
...OrchestrationMasterSlaveDataSourceFactoryBean.java	66.66% <0%> (-11.12%)	⬇️
... and 13 more

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