[Android] Refine the pause/resume behavior for packaged web app

* Pause all timers when the activity is paused, and resume them when the
  activity is resumed.
* Add boolean flag to indicate if the timers are paused or XWalkView is hidden
* Update the API documentations for pauseTimers/resumeTimers are also

BUG=https://crosswalk-project.org/jira/browse/XWALK-1603
[Runtime] Enable the folder based i18n support for WGT package.

The WGT folder based i18n support based on system locale setting and
application default locale setting (in config.xml), this patch will
enable to load resources by these locale settings.

For more details, please refer to
http://www.w3.org/TR/widgets/#folder-based-localization

The related bug is https://crosswalk-project.org/jira/browse/XWALK-1030
[Tizen][Runtime] Fix using the wrong attribute name for hardware key setting.

In Tizen, the <tizen:setting hwkey-event="disable" /> setting could
disable the hardware key event. But the implementation use the wrong
attribute name "hwkey", need to change it to "hwkey-event" according to
Tizen core spec feature XWALK-1491.

BUG=XWALK-1611
[Android] Force using ContentVideoViewLegacy to make the android fullscreen video works.

Currently the default ContentVideoView in upstream is not ready for production usage. Bugs
are many about focus related. We turn to use ContentVideoViewLegacy now and when bug in
chromium is fixed, will revert the change.

BUG=https://crosswalk-project.org/jira/browse/XWALK-1608
[Runtime] Fix i18n data loss BUG when storage to db

We get manifest from file first time after application
installed, and we storage this manifest data to db, after
that we will get manifest data from db.

We parse i18n items into i18n_data_ and remove they from
data_, But we only storage data_ in db, so we can not get
i18n items after we reload the manifest data from db.
Merge pull request #1880 from hmin/timers

[Android] Refine the pause/resume behavior for packaged web app
Merge pull request #1886 from sqliu/fix-fullscreen-video

[Android] Force using ContentVideoViewLegacy to make the android fullscr...
Merge pull request #1892 from takethathe/hwkey-event

[Tizen][Runtime] Fix using the wrong attribute name for hardware key setting.
Merge pull request #1893 from yeyuyinjie/fix_manifest_data

[Runtime] Fix i18n data loss BUG when storage to db
Merge pull request #1879 from takethathe/i18n-folder

[Runtime] Enable the folder based i18n support for WGT package.