[SCB-1825] client outlog: rename item and delete README.md

[heyile]

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[coveralls]

Coverage remained the same at 84.984% when pulling 099aca4 on heyile:scb-1796 into 6cef5fe on apache:master.

[liubao68]

I created a new issue to track this refactoring and the old is already closed in previous version.