Add a struct for signer config
Add a struct for signer config

We can use a struct of config to hold all the necessary info that needed
to run a notary signer.

Signed-off-by: Hu Keping <ce660952c949ad2751377b45317337be332e80ac@huawei.com>

BSWANG/denverdino.github.io,denverdino/docker.github.io,andrewhsu/notary,shubheksha/docker.github.io,gdevillele/docker.github.io,vdemeester/notary,JimGalasyn/docker.github.io,andrewhsu/notary,joaofnfernandes/docker.github.io,menglingwei/denverdino.github.io,docker/docker.github.io,londoncalling/docker.github.io,denverdino/docker.github.io,shin-/docker.github.io,gdevillele/docker.github.io,gdevillele/docker.github.io,bdwill/docker.github.io,thaJeztah/docker.github.io,docker/notary,jfrazelle/notary,joeuo/docker.github.io,jfrazelle/notary,denverdino/denverdino.github.io,shin-/docker.github.io,shin-/docker.github.io,joeuo/docker.github.io,dqminh/notary,johnsandiford/notary,rillig/docker.github.io,anweiss/docker.github.io,jzwlqx/denverdino.github.io,bdwill/docker.github.io,menglingwei/denverdino.github.io,shubheksha/docker.github.io,shin-/docker.github.io,phiroict/docker,troy0820/docker.github.io,johnstep/docker.github.io,endophage/notary,danix800/docker.github.io,sanscontext/docker.github.io,anweiss/docker.github.io,phiroict/docker,thaJeztah/docker.github.io,jfrazelle/notary,denverdino/docker.github.io,docker-zh/docker.github.io,andrewhsu/notary,joeuo/docker.github.io,anweiss/docker.github.io,cyli/notary,londoncalling/docker.github.io,docker/notary,docker-zh/docker.github.io,cyli/notary,sanscontext/docker.github.io,denverdino/denverdino.github.io,phiroict/docker,johnstep/docker.github.io,danix800/docker.github.io,shubheksha/docker.github.io,docker/docker.github.io,menglingwei/denverdino.github.io,troy0820/docker.github.io,endophage/notary,dqminh/notary,londoncalling/docker.github.io,thaJeztah/docker.github.io,thaJeztah/docker.github.io,thaJeztah/docker.github.io,vdemeester/notary,bdwill/docker.github.io,LuisBosquez/docker.github.io,umayr/notary,sanscontext/docker.github.io,londoncalling/docker.github.io,umayr/notary,bdwill/docker.github.io,HuKeping/notary,londoncalling/docker.github.io,HuKeping/notary,joaofnfernandes/docker.github.io,aduermael/docker.github.io,alexisbellido/docker.github.io,gdevillele/docker.github.io,sanscontext/docker.github.io,denverdino/denverdino.github.io,jzwlqx/denverdino.github.io,LuisBosquez/docker.github.io,LuisBosquez/docker.github.io,docker/docker.github.io,troy0820/docker.github.io,umayr/notary,johnstep/docker.github.io,BSWANG/denverdino.github.io,denverdino/docker.github.io,docker-zh/docker.github.io,aduermael/docker.github.io,alexisbellido/docker.github.io,HuKeping/notary,aduermael/docker.github.io,menglingwei/denverdino.github.io,BSWANG/denverdino.github.io,aduermael/docker.github.io,docker/docker.github.io,docker-zh/docker.github.io,jzwlqx/denverdino.github.io,endophage/notary,alexisbellido/docker.github.io,joaofnfernandes/docker.github.io,danix800/docker.github.io,LuisBosquez/docker.github.io,joeuo/docker.github.io,johnstep/docker.github.io,denverdino/denverdino.github.io,BSWANG/denverdino.github.io,shubheksha/docker.github.io,rillig/docker.github.io,shin-/docker.github.io,phiroict/docker,johnstep/docker.github.io,phiroict/docker,vdemeester/notary,anweiss/docker.github.io,JimGalasyn/docker.github.io,joeuo/docker.github.io,jzwlqx/denverdino.github.io,gdevillele/docker.github.io,denverdino/docker.github.io,alexisbellido/docker.github.io,docker-zh/docker.github.io,sanscontext/docker.github.io,LuisBosquez/docker.github.io,JimGalasyn/docker.github.io,JimGalasyn/docker.github.io,rillig/docker.github.io,troy0820/docker.github.io,docker/notary,anweiss/docker.github.io,menglingwei/denverdino.github.io,bdwill/docker.github.io,danix800/docker.github.io,shubheksha/docker.github.io,dqminh/notary,jzwlqx/denverdino.github.io,alexisbellido/docker.github.io,docker/docker.github.io,joaofnfernandes/docker.github.io,rillig/docker.github.io,johnsandiford/notary,joaofnfernandes/docker.github.io,BSWANG/denverdino.github.io,denverdino/denverdino.github.io,johnsandiford/notary,JimGalasyn/docker.github.io,cyli/notary