[usecase-webapi] Improve WebSocket usecase

- Add the 'Connect' button and 'Disconnect' button

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 #694 from yunxliu/yunxliu/misc/webSocket_modify

[usecase-webapi] Improve WebSocket usecase