[Android] Add the check of application launch path in packaging tool.

   Since there is no prompt when there is no application launch path
in the manifest.json file, to improve the user experience of crosswalk,
in the packaging tool, add the check of application launch path in packaging
tool. The related test case is added.

BUG=https://crosswalk-project.org/jira/browse/XWALK-645
Merge pull request #1290 from ShDavidliu/packaging_manifest

[Android] Add the check of application launch path in packaging tool.