externalize application-github.properties and apollo-env.properties

[nobodyiam]

By externalizing application-github.properties and apollo-env.properties, we could upload apollo-configservice, apollo-adminservice and apollo-portal installation files with releases.

So our users don't need to package them locally anymore, instead they could simply download them from our releases, do some simple configuration, and start apollo services easily!

[codecov-io]

Codecov Report

Merging #1273 into master will decrease coverage by 0.05%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master    #1273      +/-   ##
============================================
- Coverage     49.01%   48.95%   -0.06%     
+ Complexity     1701     1698       -3     
============================================
  Files           366      366              
  Lines         10277    10277              
  Branches       1043     1043              
============================================
- Hits           5037     5031       -6     
- Misses         4868     4873       +5     
- Partials        372      373       +1

Impacted Files	Coverage Δ	Complexity Δ
...work/apollo/biz/message/DatabaseMessageSender.java	56.25% <0%> (-10.42%)	6% <0%> (-2%)
.../apollo/internals/RemoteConfigLongPollService.java	77.3% <0%> (-0.62%)	27% <0%> (-1%)

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[coveralls]

Coverage decreased (-0.05%) to 52.583% when pulling da1ccae on nobodyiam:externalize-meta-service-and-db-properties-file into 16bf9e9 on ctripcorp:master.