[usecase-webapi] Improve Clipboard usecase

- Modify button name "Launch" to "Launch clipboard test" and remove button "Retest"

Impacted TCs num(approved): New 0, Update 1, Delete 0
Unit test Platform: [Andriod]
Test result summary: Pass 1, Fail 0, Blocked 0
[usecase-webapi] Improve Viewport usecase.

Impacted tests(approved): New 0, Update 1, Delete 0
Unit test platform: [Tizen IVI]
Unit test result summary: Pass 1, Fail 0, Block 0
[usecase-webapi] Improve WebSpeech usecase

- Adjust the case with screen view
- Failure analysis: Could not connect to speech recognition service

Impacted tests(approved): new 0, update 1, delete 0
Unit test platform: [Tizen IVI]
Unit test result summary: pass 0, fail 1, block 0
[usecase-webapi] Improve WebRTC usecase

- Adjust the case with screen view
- Failure analysis: https://crosswalk-project.org/jira/browse/XWALK-1535

Impacted tests(approved): new 0, update 1, delete 0
Unit test platform: [Tizen IVI]
Unit test result summary: pass 0, fail 1, block 0
[usecase-webapi] Improve RawSockets usecase

- Adjust the case with screen view

Impacted tests(approved): new 0, update 1, delete 0
Unit test platform: [Tizen IVI]
Unit test result summary: pass 1, fail 0, block 0
Merge pull request #583 from zhangjingx/zhangjingx/misc/clipboard

[usecase-webapi] Improve Clipboard usecase
Merge pull request #584 from minxhuang/hm/misc/usecase-w3c/Viewport-hotfix

[usecase-webapi] Improve Viewport usecase.
Merge pull request #589 from yunxliu/yunxliu/misc/rawSockets

[usecase-webapi] Improve RawSockets usecase
Merge pull request #591 from yunxliu/yunxliu/misc/webSpeech

[usecase-webapi] Improve WebSpeech usecase
Merge pull request #593 from yunxliu/yunxliu/misc/webrtc_update

[usecase-webapi] Improve WebRTC usecase