[Android] Update xwalk_app_template after shared layer move into core

The main changes are:
1. There is no xwalk_runtime_java.jar any more.
2. Split xwalk_core_library_java.jar into app part and library part
   to support shared mode.
For aar package, since it on accepts one classes.jar, still create
xwalk_core_library_java.jar and pass it as argument when creating
aar package.

BUG=https://crosswalk-project.org/jira/browse/XWALK-2537
How about just using `(os.path.join(options.target, 'lib.java', 'xwalk_core_library_java.jar'), 'classes.jar')` here? I'd rather avoid introducing another command line option if possible, it can easily create a mess where it's hard to find out what each script is actually using.