[usecase-embeddingapi] Improve XWalkPrefere and multi views usecase

- Improve MultiSurfaceViewsActivity, MultiTextureViewsActivity and XWalkPrefere

Impacted tests(approved): new 0, update 3, delete 0
Unit test platform: [Android]
Unit test result summary: pass 3, fail 0, block 0
[doc]Add dev/user readme
[usecase-wrt]Add Readme file
[usecase-cordova] Add README.md for cordova usecase
[wrt-usecase] Add readme files to subcase
Merge pull request #987 from linshen/shenlin/usrcase/add_readme

[usecase-wrt]Add Readme file
Merge pull request #983 from wanghongjuan/wanghongjuan/usecase/readme

[wrt-usecase] Add readme files to subcase
Merge pull request #982 from haoxli/haoxli/usecase/cordova-readme

[usecase-cordova] Add README.md for cordova usecase
Merge pull request #988 from linshen/shenlin/adddocreadme

[doc]Add WRT dev/user readme
[wrt-usecase] Update TCs for OpenFile

Impacted TCs num(approved): New 0, Update 2, Delete 0
Unit test Platform: Android
Android test result summary: Pass 2, Fail 0, Block 0
[wrt][xwalk-2298] Add controls to securitymanu app

Impacted TCs num(approved): New 0, Update 1, Delete 0
Unit test Platform: Android
Android test result summary: Pass 1, Fail 0, Block 0
[wrt-usecase] Update manifest files to new template

Impacted TCs num(approved): New 0, Update 11, Delete 0
Unit test Platform: Android
Android test result summary: Pass 11, Fail 0, Block 0
Merge pull request #974 from zhuyongyong/yongzhu/usecase-embeddingapi/improveInfo

[usecase-embeddingapi] Improve XWalkPrefere and multi views usecase
Merge pull request #993 from wanghongjuan/wanghongjuan/usecase/update-manifest

[wrt-usecase] Update manifest files to new template
Merge pull request #992 from wanghongjuan/wanghongjuan/wrt/xwalk-2298

[wrt][xwalk-2298] Add controls to securitymanu app
Merge pull request #991 from wanghongjuan/wanghongjuan/usecase/OpenFile

[wrt-usecase] Update TCs for OpenFile