[usecase-webapi] Add README.md for webapi usecase
[usecase-embeddingapi] Add README.md for embeddingAPI usecase

- Add embeddingapi-usecase-tests/src/org/xwalk/embedded/api/sample/READ.md
- Rename embeddingapi-usecase-tests/README to embeddingapi-usecase-tests/README.md
[webapi-usecase] add usecase README file for description

- Add 18 usecase README.md to describe basic funtionalities and covering methods
[webapi] Update use case for new rule
[usecase-wrt][XWALK-1172]Add applicton protection tcs

[Detailed commit message (if have)]
Impacted TCs num(designed): New 1, update 0, deleted 0
Unit test platform: [tizen]
Merge pull request #999 from linshen/shenlin/application-protection-xwalk-1172

[usecase-wrt][XWALK-1172]Add applicton protection tcs
Merge pull request #986 from xinliux/xinliux/usecase/README

[webapi-usecase] add usecase README file for description
Merge pull request #972 from zhuyongyong/yongzhu/usecase-embeddingapi/addReadMe

[usecase-embeddingapi] Add README.md for embeddingAPI usecase
Merge pull request #985 from yunxliu/yunxliu/misc/usecase_readme

[usecase-webapi] Add README.md for webapi usecase
Merge pull request #997 from yunxiaoxie/yunxiaoxie/speechsynthesisnewrule

[webapi] Update use case for new rule