Replace filter interface

[mark4z]

What this PR does:

Which issue(s) this PR fixes:

Fixes #108

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

[codecov-io]

Codecov Report

Merging #109 (b434c39) into develop (a654db8) will decrease coverage by 0.47%.
The diff coverage is 68.75%.

@@             Coverage Diff             @@
##           develop     #109      +/-   ##
===========================================
- Coverage    41.84%   41.36%   -0.48%     
===========================================
  Files           33       33              
  Lines         1410     1378      -32     
===========================================
- Hits           590      570      -20     
+ Misses         736      730       -6     
+ Partials        84       78       -6     

Impacted Files	Coverage Δ
pkg/client/dubbo/dubbo.go	22.01% <ø> (ø)
pkg/client/mapper.go	78.94% <ø> (ø)
pkg/client/request.go	0.00% <ø> (ø)
pkg/filter/accesslog/access_log.go	4.08% <ø> (ø)
pkg/filter/recovery/recovery.go	77.77% <ø> (ø)
pkg/filter/replacepath/replace_path.go	61.11% <ø> (ø)
pkg/filter/response/response.go	5.38% <0.00%> (ø)
pkg/registry/util.go	0.00% <ø> (ø)
pkg/router/api.go	100.00% <ø> (ø)
pkg/client/http/http.go	60.31% <33.33%> (ø)
... and 9 more

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