[Android] Restore the function for '--icon'.

This patch is to restore the function for '--icon'.
If the developer specify the icon in the command line, this icon
will be used instead of the icons in manifest.json.

BUG=https://crosswalk-project.org/jira/browse/XWALK-1368
Merge pull request #1799 from wuhengzhi/multi_icon_refine

[Android] Restore the function for '--icon'.