[usecase-webapi] Improve content usecase

- Scan complete to a pop up, not open in new page.
- Organize result to a table.
- Default show get Directory result.
- Update the button to "Open Dir".
- Fail Reason: DB connection error.

Impacted TCs num: New 0, Update 1, Delete 0
Unit test Platform: [Tizen-IVI]
Test result summary: Pass 0, Fail 1, Blocked 0
[misc] Integrate latest testharness.js framework into system tests

- http://github.com/w3c/testharness.js/
- commit b8c9ce09cd031e8a732bbfc0a8c81f674ffa8a49
[misc] Integrate W3C navigator.language test case

https://github.com/w3c/web-platform-tests/blob/master/workers/interfaces/WorkerUtils/navigator/language.html

BUG=https://crosswalk-project.org/jira/browse/XWALK-2242
[behavior] Add subcase in tests xml

- Add subcase attribute in <testcase>
- Remove redundant element for behavior
[embedding][XWALK-1040] Add new embedding api tests for crosswalk

- use crosswalk-webview instead of xwalk_core_library in the README and pack.sh
- Add 24 cases about tests for embedding api. 10 of them are for XWalkExtension interface, others are for XWalkUIClient interface.
- Failure analysis:6 cases are failed because the methods of embedding api are not exist.

Impacted tests(approved): new 24, update 0, delete 0
Unit test platform: [Android]
Unit test result summary: pass 18, fail 6, block 0
Merge pull request #646 from JianfengXu/xujf/content/update

[usecase-webapi] Improve content usecase
Merge pull request #632 from haoxli/haoxli/behavior/subcase

[behavior] Add subcase in tests xml
Merge pull request #618 from zhuyongyong/yongzhu/embeddingAPI/add

[embedding][XWALK-1040] Add new embedding api tests for crosswalk
[wrt] Modify xpk to wgt and script
Merge pull request #672 from wanghongjuan/wanghongjuan/wrt/test

[wrt] Modify xpk to wgt and script
[misc] Remove '<!-- -->' from the start of .html file as workaround

BUG=https://crosswalk-project.org/jira/browse/XWALK-2293
This shall be a Crosswalk implementation issue, maybe Chromium's.
Merge pull request #682 from zqzhang/zqzhang/navigator-language-w3c

[misc][XWALK-2242] Integrate W3C navigator.language test case