[demo-express] Merge 4 tests to demo express from usecase

- Merge Download, SystemInfo, SystemSettingIncomingCall and SystemSettingScreen to demo from usecase
- Download: Download folder default as N/A
- SystemSetting IncomingCall: No audio file default as N/A, click button adding error note
- SyttemSeting Screen: No picture file default as N/A, click button adding error note
[demo-express] Add 3 samples to demo express.

- Fail Reason: XWALK-2401, XWALK-2100

Impacted TCs num(approved): New 3, Update 0, Delete 0
Unit test Platform: [Tizen-IVI]
Unit test result summary: Pass 1, Fail 2, Blocked 0
[demo-express] Move usecase to demo-express

- Move usecase to demo-express
- Failure analysis: https://crosswalk-project.org/jira/browse/XWALK-1954
                    https://crosswalk-project.org/jira/browse/XWALK-1266

Impacted tests(approved): new 0, update 4, delete 0
Unit test platform: [Tizen IVI]
Unit test result summary: pass 2, fail 2, block 0
Merge pull request #11 from xinliux/xinliux/merge-from-usecase

[demo-express] Merge 4 tests to demo express from usecase
Merge pull request #12 from JianfengXu/xujf/sample/add

[demo-express] Add 3 samples to demo express.
Merge pull request #13 from yunxliu/yunxliu/samples/move

[demo-express] Move usecase to demo-express