[Android] Packaging tool fail to run with python3.*.

1. Change the print statement to print function.
2. Add encoding when handling the file with python.
Merge pull request #1670 from junmin-zhu/python3

[Android] Packaging tool fail to run with python3.*.
Merge pull request #1667 from shaochangbin/content-src-issue

[Runtime] Fix launch issue for widget applications that don't have 'content' element in config.xml.
[Runtime] Add widget manifest handler.
[Runtime] Implement Widget API.