Add: Split config center GetConfig method

[zouyx]

What this PR does:

1.Split config center GetConfig method to getRule/getinternalproperty/getProperties for different scenarios

• getRule: get router rule (useless now)
• getinternalProperty:get value for specify key and group
• getProperties : get full properties file for specify key

2.Add app_id config item for apollo config center

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

[codecov-io]

Codecov Report

Merging #267 into develop will increase coverage by 0.02%.
The diff coverage is 55%.

@@             Coverage Diff             @@
##           develop     #267      +/-   ##
===========================================
+ Coverage     65.5%   65.53%   +0.02%     
===========================================
  Files          111      111              
  Lines         7038     7041       +3     
===========================================
+ Hits          4610     4614       +4     
+ Misses        1972     1970       -2     
- Partials       456      457       +1

Impacted Files	Coverage Δ
config/config_center_config.go	71.42% <100%> (+2.19%)	⬆️
config/base_config.go	64.61% <100%> (ø)	⬆️
config_center/zookeeper/impl.go	39.58% <20%> (-0.85%)	⬇️
config_center/apollo/impl.go	87.01% <58.33%> (ø)	⬆️
cluster/cluster_impl/failback_cluster_invoker.go	78.49% <0%> (-2.16%)	⬇️
remoting/zookeeper/listener.go	46.9% <0%> (-1.04%)	⬇️
remoting/zookeeper/client.go	63.87% <0%> (-0.58%)	⬇️
cluster/cluster_impl/base_cluster_invoker.go	71.69% <0%> (+16.98%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 0add5c9...bd7d791. Read the comment docs.

[fangyincheng]

LGTM

[hxmhlt]

LGTM