[Android] Fix Python 3 compatibility issue in packaging tools.

* Fix the open file mode which will cause str type error in Python 3
* Use sys.maxsize instead of sys.maxint since sys.maxint is remove in Python 3

BUG=https://crosswalk-project.org/jira/browse/XWALK-1721
Merge pull request #1966 from sqliu/fix-python3

[Android] Fix Python 3 compatibility issue in packaging tools.
[Runtime] Add getter and setter support for widget preferences api

According to
http://dev.w3.org/2006/waf/widgets-api/#the-preferences-attribute
the preference items need to support getter and setter.

And if we storage getter and setter items in WidgetStorage
entity, we will produce a dead loop like :
getter=> return this[itemKey] => getter => ...
So we storage getter and setter items in _itemStorage to
avoid this dead loop.
[Runtime] Fix identify the app package type while loading it.

Current implementation identify package type by configure document
name, 'manifest.json' will be recognized as XPK package, and
'config.xml' will be WGT package, but it's not always right if both
'manifest.json' and 'config.xml' exist in one package.

This patch add a package type parameter when loading it, to make sure
that unpacking and parsing package use the same package type.
Merge pull request #1972 from CooderIan/preferences_getter_setter

[Runtime] Add getter and setter support for widget
Merge pull request #1957 from takethathe/package-type

[Runtime] Fix identify the app package type while loading it.
Bump version to 7.35.141.0